[PATCH] Add kerneldocs for some functions in mm/memory.c

These functions are already documented quite well with long comments.  Now
add kerneldoc style header to make this turn up in everyones favorite doc
format.

Signed-off-by: Rolf Eike Beer <eike-kernel@sf-tec.de>
Cc: "Randy.Dunlap" <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>