[PATCH] x86_64: Implemenent machine_emergency_restart

It is not safe to call set_cpus_allowed() in interrupt
context and disabling the apics is complicated code.
So unconditionally skip machine_shutdown in machine_emergency_reboot
on x86_64.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>