lib/bitmap.c: fix kernel-doc notation

Fix new kernel-doc warnings in lib/bitmap.c:

  Warning(lib/bitmap.c:596): No description found for parameter 'buf'
  Warning(lib/bitmap.c:596): Excess function parameter 'bp' description in '__bitmap_parselist'

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>