powerpc/4xx: Add suspend and idle support

Add suspend/resume support for 4xx compatible CPUs.
See /sys/power/state for available power states configured in.

Add two different idle states (idle-wait and idle-doze) controlled via sysfs.
Default is idle-wait.
	cat /sys/devices/system/cpu/cpu0/idle
	[wait] doze

To save additional power, use idle-doze.
	echo doze > /sys/devices/system/cpu/cpu0/idle
	cat /sys/devices/system/cpu/cpu0/idle
	wait [doze]

Signed-off-by: Victor Gallardo <vgallardo@apm.com>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>