x86, mce: unify, prepare codes

Move current 32-bit mce_32.c code into mce_64.c.

[ Remove unused artifact stop/restart_mce pointed by Andi Kleen ]

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Andi Kleen <ak@firstfloor.org>
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>