lib/bitmap.c: micro-optimization for __bitmap_complement()

lib/bitmap.c: micro-optimization for __bitmap_complement()

Use BITS_TO_LONGS() macro to avoid calculation of reminder (bits %
BITS_PER_LONG) On ARM64 it saves 5 instruction for function - 16 before
and 11 after.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Yury Norov <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Rasmus Villemoes <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>