[PATCH] x86_64: CONFIG_BUG=n fixes

Fixes some !CONFIG_BUG warnings:
include/asm/mmu_context.h: I funktion `switch_mm':
include/asm/mmu_context.h:57: varning: implicit declaration of function `out_of_line_bug'

Signed-off-by: Alexander Nyberg <alexn@telia.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>