[PATCH] pcwd.c: Call kernel_power_off not machine_power_off

The call appears to come from process context so kernel_power_off
should be safe.  And acpi_power_off won't necessarily work if you just
call machine_power_off.

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