linux/mm.h provides offset_in_page() macro.  Let's use already predefined
macro instead of (addr & ~PAGE_MASK).
Signed-off-by: NAlexander Kuleshov <kuleshovmail@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>