Drop the exporting of empty <linux/byteorder/generic.h>

Fix up the contents of <linux/byteorder/> so that it doesn't export a
content-free generic.h to user space. This involves:

* Removing the __KERNEL__ tests from generic.h and dropping it from
Kbuild.
* Wrapping the inclusions of generic.h in both big_endian.h and
little_endian.h in __KERNEL__ tests.
* Shifting big_endian.h and little_endian.h from header-y to
unifdef-y in Kbuild.

Signed-off-by: Robert P. J. Day <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/byteorder/Kbuild

···
-header-y += big_endian.h
-header-y += little_endian.h
-
-unifdef-y += generic.h
+unifdef-y += big_endian.h
+unifdef-y += little_endian.h
 unifdef-y += swab.h

include/linux/byteorder/big_endian.h

···
 #define __cpu_to_be16s(x) do {} while (0)
 #define __be16_to_cpus(x) do {} while (0)
 
+#ifdef __KERNEL__
 #include <linux/byteorder/generic.h>
+#endif
 
 #endif /* _LINUX_BYTEORDER_BIG_ENDIAN_H */

include/linux/byteorder/generic.h

···
  *
  */
 
-
-#if defined(__KERNEL__)
-/*
- * inside the kernel, we can use nicknames;
- * outside of it, we must avoid POSIX namespace pollution...
- */
 #define cpu_to_le64 __cpu_to_le64
 #define le64_to_cpu __le64_to_cpu
 #define cpu_to_le32 __cpu_to_le32
···
 {
 	*var = cpu_to_be64(be64_to_cpu(*var) + val);
 }
-
-#endif /* KERNEL */
 
 #endif /* _LINUX_BYTEORDER_GENERIC_H */

include/linux/byteorder/little_endian.h

···
 #define __cpu_to_be16s(x) __swab16s((x))
 #define __be16_to_cpus(x) __swab16s((x))
 
+#ifdef __KERNEL__
 #include <linux/byteorder/generic.h>
+#endif
 
 #endif /* _LINUX_BYTEORDER_LITTLE_ENDIAN_H */