[PATCH] kernel-doc: mm/readhead fixup

Put short function description for read_cache_pages() on one line as needed
by kernel-doc.

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