powerpc/mpc5200: Fix lite5200b suspend/resume

Suspend/resume ("echo mem > /sys/power/state") does not work with
vanilla kernels -- the system does not suspend correctly and just
hangs. This patch fixes this so suspend/resume works:

1) of_iomap does not map the whole 0xC000 of the MPC5200 immr so
saving registers does not work.
2) PCI registers need to be saved and restored.

Signed-off-by: Tim Yamin <plasm@roo.me.uk>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>