[POWERPC] Fixup MPC8568 dts

The PCI nodes on the MPC8568 dts didn't get moved up to be sibilings of the
SOC node when we did that clean up for some reason.  Fix that up and some
minor whitespace and adjusting the size of the soc reg property.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>