Low-power mode implementation for Lite5200b.
Some I/O registers are also saved here.

A recent U-Boot that supports this (lite5200b_PM_config) is needed.
Signed-off-by: NDomen Puncer <domen.puncer@telargo.com>
Signed-off-by: NSylvain Munaut <tnt@246tNt.com>
Signed-off-by: NPaul Mackerras <paulus@samba.org>