machine_halt() managed to trigger the soft lockup detection due to not
disabling interrupts before going to sleep, so correct that.

machine_power_off() should be using pm_power_off, which lets us drop the
board-specific hacks from here.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>