Documentation: boot.rst: fix warnings

Fix WARNING: Inline emphasis start-string without end-string.
This warning was due to wrong syntax being used.

Signed-off-by: Daniel W. S. Almeida <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jonathan Corbet <[e-mail]>

Documentation/x86/boot.rst

···
   chunks of memory are occupied by kernel data.
 
   Thus setup_indirect struct and SETUP_INDIRECT type were introduced in
-  protocol 2.15.
+  protocol 2.15::
 
-  struct setup_indirect {
-    __u32 type;
-    __u32 reserved;  /* Reserved, must be set to zero. */
-    __u64 len;
-    __u64 addr;
-  };
+    struct setup_indirect {
+      __u32 type;
+      __u32 reserved;  /* Reserved, must be set to zero. */
+      __u64 len;
+      __u64 addr;
+    };
 
   The type member is a SETUP_INDIRECT | SETUP_* type. However, it cannot be
   SETUP_INDIRECT itself since making the setup_indirect a tree structure
···
   and stack space can be limited in boot contexts.
 
   Let's give an example how to point to SETUP_E820_EXT data using setup_indirect.
-  In this case setup_data and setup_indirect will look like this:
+  In this case setup_data and setup_indirect will look like this::
 
-  struct setup_data {
-    __u64 next = 0 or <addr_of_next_setup_data_struct>;
-    __u32 type = SETUP_INDIRECT;
-    __u32 len = sizeof(setup_data);
-    __u8 data[sizeof(setup_indirect)] = struct setup_indirect {
-      __u32 type = SETUP_INDIRECT | SETUP_E820_EXT;
-      __u32 reserved = 0;
-      __u64 len = <len_of_SETUP_E820_EXT_data>;
-      __u64 addr = <addr_of_SETUP_E820_EXT_data>;
+    struct setup_data {
+      __u64 next = 0 or <addr_of_next_setup_data_struct>;
+      __u32 type = SETUP_INDIRECT;
+      __u32 len = sizeof(setup_data);
+      __u8 data[sizeof(setup_indirect)] = struct setup_indirect {
+        __u32 type = SETUP_INDIRECT | SETUP_E820_EXT;
+        __u32 reserved = 0;
+        __u64 len = <len_of_SETUP_E820_EXT_data>;
+        __u64 addr = <addr_of_SETUP_E820_EXT_data>;
+      }
     }
-  }
 
 .. note::
      SETUP_INDIRECT | SETUP_NONE objects cannot be properly distinguished
···
 All kernel_info data should be part of this structure. Fixed size data have to
 be put before kernel_info_var_len_data label. Variable size data have to be put
 after kernel_info_var_len_data label. Each chunk of variable size data has to
-be prefixed with header/magic and its size, e.g.:
+be prefixed with header/magic and its size, e.g.::
 
   kernel_info:
           .ascii  "LToP"          /* Header, Linux top (structure). */