[PATCH] Add faster __iowrite32_copy routine for x86_64

This assembly version is measurably faster than the generic version in
lib/iomap_copy.c.

Signed-off-by: Bryan O'Sullivan <bos@pathscale.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>