lib/bitmap.c make bitmap_print_bitmask_to_buf parseable

The documentation of such function is not on a proper ReST format,
as reported by Sphinx:

    Documentation/core-api/kernel-api:81: ./lib/bitmap.c:532: WARNING: Unexpected indentation.
    Documentation/core-api/kernel-api:81: ./lib/bitmap.c:526: WARNING: Inline emphasis start-string without end-string.
    Documentation/core-api/kernel-api:81: ./lib/bitmap.c:532: WARNING: Inline emphasis start-string without end-string.
    Documentation/core-api/kernel-api:81: ./lib/bitmap.c:532: WARNING: Inline emphasis start-string without end-string.
    Documentation/core-api/kernel-api:81: ./lib/bitmap.c:533: WARNING: Block quote ends without a blank line; unexpected unindent.
    Documentation/core-api/kernel-api:81: ./lib/bitmap.c:536: WARNING: Definition list ends without a blank line; unexpected unindent.
    Documentation/core-api/kernel-api:81: ./lib/bitmap.c:542: WARNING: Unexpected indentation.
    Documentation/core-api/kernel-api:81: ./lib/bitmap.c:536: WARNING: Inline emphasis start-string without end-string.
    Documentation/core-api/kernel-api:81: ./lib/bitmap.c:536: WARNING: Inline emphasis start-string without end-string.
    Documentation/core-api/kernel-api:81: ./lib/bitmap.c:543: WARNING: Block quote ends without a blank line; unexpected unindent.
    Documentation/core-api/kernel-api:81: ./lib/bitmap.c:552: WARNING: Unexpected indentation.
    Documentation/core-api/kernel-api:81: ./lib/bitmap.c:545: WARNING: Inline emphasis start-string without end-string.
    Documentation/core-api/kernel-api:81: ./lib/bitmap.c:545: WARNING: Inline emphasis start-string without end-string.
    Documentation/core-api/kernel-api:81: ./lib/bitmap.c:552: WARNING: Inline emphasis start-string without end-string.
    Documentation/core-api/kernel-api:81: ./lib/bitmap.c:552: WARNING: Inline emphasis start-string without end-string.
    Documentation/core-api/kernel-api:81: ./lib/bitmap.c:554: WARNING: Block quote ends without a blank line; unexpected unindent.
    Documentation/core-api/kernel-api:81: ./lib/bitmap.c:556: WARNING: Definition list ends without a blank line; unexpected unindent.
    Documentation/core-api/kernel-api:81: ./lib/bitmap.c:580: WARNING: Unexpected indentation.

So, the produced output at:

	https://www.kernel.org/doc/html/latest/core-api/kernel-api.html?#c.bitmap_print_bitmask_to_buf



is broken. Fix it by adding spaces and marking the literal blocks.

Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>