powerpc/85xx: Refactor mpc8548cds device tree

* Create mpc8548cds.dtsi
* Move lbc, soc and pci0 nodes to mpc8548cds_32b.dtsi
* Change cuImage.mpc8548cds to cuImage.mpc8548cds_32b
* Rename mpc8548cds.dts to mpc8548cds_32b.dts

Signed-off-by: Zhao Chenhui <chenhui.zhao@freescale.com>
Signed-off-by: Li Yang <leoli@freescale.com>
Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>