docs: packing: move it to core-api book and adjust markups

The packing.txt file was misplaced, as docs should be part of
a documentation book, and not at the root dir.

So, move it to the core-api directory and add to its index.

Also, ensure that the file will be properly parsed and the bitmap
ascii artwork will use a monotonic font.

Fixes: 554aae35007e ("lib: Add support for generic packing operations")
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>
Reviewed-by: Vladimir Oltean <[e-mail]>
Tested-by: Vladimir Oltean <[e-mail]>
Reviewed-by: Mike Rapoport <[e-mail]>
Signed-off-by: Jonathan Corbet <[e-mail]>

Documentation/core-api/index.rst

···
    librs
    genalloc
    errseq
+   packing
    printk-formats
    circular-buffers
    generic-radix-tree

Documentation/packing.txt Documentation/core-api/packing.rst

···
 ------------
 
 This API deals with 2 basic operations:
+
   - Packing a CPU-usable number into a memory buffer (with hardware
     constraints/quirks)
   - Unpacking a memory buffer (which has hardware constraints/quirks)
···
 
 1. Normally (no quirks), we would do it like this:
 
-63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32
-7                       6                       5                        4
-31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10  9  8  7  6  5  4  3  2  1  0
-3                       2                       1                        0
+::
+
+  63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32
+  7                       6                       5                        4
+  31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10  9  8  7  6  5  4  3  2  1  0
+  3                       2                       1                        0
 
 That is, the MSByte (7) of the CPU-usable u64 sits at memory offset 0, and the
 LSByte (0) of the u64 sits at memory offset 7.
···
 
 2. If QUIRK_MSB_ON_THE_RIGHT is set, we do it like this:
 
-56 57 58 59 60 61 62 63 48 49 50 51 52 53 54 55 40 41 42 43 44 45 46 47 32 33 34 35 36 37 38 39
-7                       6                        5                       4
-24 25 26 27 28 29 30 31 16 17 18 19 20 21 22 23  8  9 10 11 12 13 14 15  0  1  2  3  4  5  6  7
-3                       2                        1                       0
+::
+
+  56 57 58 59 60 61 62 63 48 49 50 51 52 53 54 55 40 41 42 43 44 45 46 47 32 33 34 35 36 37 38 39
+  7                       6                        5                       4
+  24 25 26 27 28 29 30 31 16 17 18 19 20 21 22 23  8  9 10 11 12 13 14 15  0  1  2  3  4  5  6  7
+  3                       2                        1                       0
 
 That is, QUIRK_MSB_ON_THE_RIGHT does not affect byte positioning, but
 inverts bit offsets inside a byte.
···
 
 3. If QUIRK_LITTLE_ENDIAN is set, we do it like this:
 
-39 38 37 36 35 34 33 32 47 46 45 44 43 42 41 40 55 54 53 52 51 50 49 48 63 62 61 60 59 58 57 56
-4                       5                       6                       7
-7  6  5  4  3  2  1  0  15 14 13 12 11 10  9  8 23 22 21 20 19 18 17 16 31 30 29 28 27 26 25 24
-0                       1                       2                       3
+::
+
+  39 38 37 36 35 34 33 32 47 46 45 44 43 42 41 40 55 54 53 52 51 50 49 48 63 62 61 60 59 58 57 56
+  4                       5                       6                       7
+  7  6  5  4  3  2  1  0  15 14 13 12 11 10  9  8 23 22 21 20 19 18 17 16 31 30 29 28 27 26 25 24
+  0                       1                       2                       3
 
 Therefore, QUIRK_LITTLE_ENDIAN means that inside the memory region, every
 byte from each 4-byte word is placed at its mirrored position compared to
···
 4. If QUIRK_MSB_ON_THE_RIGHT and QUIRK_LITTLE_ENDIAN are both set, we do it
    like this:
 
-32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63
-4                       5                       6                       7
-0  1  2  3  4  5  6  7  8   9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
-0                       1                       2                       3
+::
+
+  32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63
+  4                       5                       6                       7
+  0  1  2  3  4  5  6  7  8   9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
+  0                       1                       2                       3
 
 
 5. If just QUIRK_LSW32_IS_FIRST is set, we do it like this:
 
-31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10  9  8  7  6  5  4  3  2  1  0
-3                       2                       1                        0
-63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32
-7                       6                       5                        4
+::
+
+  31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10  9  8  7  6  5  4  3  2  1  0
+  3                       2                       1                        0
+  63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32
+  7                       6                       5                        4
 
 In this case the 8 byte memory region is interpreted as follows: first
 4 bytes correspond to the least significant 4-byte word, next 4 bytes to
···
 6. If QUIRK_LSW32_IS_FIRST and QUIRK_MSB_ON_THE_RIGHT are set, we do it like
    this:
 
-24 25 26 27 28 29 30 31 16 17 18 19 20 21 22 23  8  9 10 11 12 13 14 15  0  1  2  3  4  5  6  7
-3                       2                        1                       0
-56 57 58 59 60 61 62 63 48 49 50 51 52 53 54 55 40 41 42 43 44 45 46 47 32 33 34 35 36 37 38 39
-7                       6                        5                       4
+::
+
+  24 25 26 27 28 29 30 31 16 17 18 19 20 21 22 23  8  9 10 11 12 13 14 15  0  1  2  3  4  5  6  7
+  3                       2                        1                       0
+  56 57 58 59 60 61 62 63 48 49 50 51 52 53 54 55 40 41 42 43 44 45 46 47 32 33 34 35 36 37 38 39
+  7                       6                        5                       4
 
 
 7. If QUIRK_LSW32_IS_FIRST and QUIRK_LITTLE_ENDIAN are set, it looks like
    this:
 
-7  6  5  4  3  2  1  0  15 14 13 12 11 10  9  8 23 22 21 20 19 18 17 16 31 30 29 28 27 26 25 24
-0                       1                       2                       3
-39 38 37 36 35 34 33 32 47 46 45 44 43 42 41 40 55 54 53 52 51 50 49 48 63 62 61 60 59 58 57 56
-4                       5                       6                       7
+::
+
+  7  6  5  4  3  2  1  0  15 14 13 12 11 10  9  8 23 22 21 20 19 18 17 16 31 30 29 28 27 26 25 24
+  0                       1                       2                       3
+  39 38 37 36 35 34 33 32 47 46 45 44 43 42 41 40 55 54 53 52 51 50 49 48 63 62 61 60 59 58 57 56
+  4                       5                       6                       7
 
 
 8. If QUIRK_LSW32_IS_FIRST, QUIRK_LITTLE_ENDIAN and QUIRK_MSB_ON_THE_RIGHT
    are set, it looks like this:
 
-0  1  2  3  4  5  6  7  8   9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
-0                       1                       2                       3
-32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63
-4                       5                       6                       7
+::
+
+  0  1  2  3  4  5  6  7  8   9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
+  0                       1                       2                       3
+  32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63
+  4                       5                       6                       7
 
 
 We always think of our offsets as if there were no quirk, and we translate

MAINTAINERS

···
 S:	Supported
 F:	lib/packing.c
 F:	include/linux/packing.h
-F:	Documentation/packing.txt
+F:	Documentation/core-api/packing.rst
 
 PADATA PARALLEL EXECUTION MECHANISM
 M:	Steffen Klassert <[e-mail]>