machine_power_off on i386 and x86_64 now switch to the
boot cpu out of paranoia and because the MP Specification indicates it
is a good idea on reboot, so for those architectures it is a noop.
I can't see anything in the acpi spec that requires you to be on
the boot cpu to power off the system, so this should not be an issue
for ia64.  In addition ia64 has the altix a massive multi-node
system where switching to the boot cpu sounds insane as we may
hot removed the boot cpu.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>