[PATCH] fix list.h kernel-doc

kernel-doc:

Put all short function descriptions on one line or if they are too long,
omit the short description & add a Description: section for them.

Change some list iterator descriptions to use "current" point instead of
"existing" point.

Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>