[PATCH] x86_64: Correct wrong comment in local.h

local_t is actually a win over atomic_t because it does not need lock
prefixes.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>