Powerpc support for SBC8548 board

The following three patches add support for the Wind River SBC8548 board onto the powerpc branch. The patches are as follows:

1) Add basic support for Wind River SBC8548 as powerpc

This adds in the basic platform support file -- closely matching that which exists for the MPC8548CDS board. These are layered on top of the earlier SBC8560 patches (only is an issue for the usual Makefile/Kconfig patch collisions).

 powerpc/arch/powerpc/platforms/85xx/Kconfig   |   10 +
 powerpc/arch/powerpc/platforms/85xx/Makefile  |    1 
 powerpc/arch/powerpc/platforms/85xx/sbc8548.c |  182 ++++++++++++++++++++++++++
 3 files changed, 191 insertions(+), 2 deletions(-)

2) Add device tree source for Wind River SBC8548 board

This also closely matches what exists for the MPC8548CDS platform. The big difference here is that this board doesn't have physical access to PCI#2 and it doesn't have the CDS's bridges, i8259, peripherals, etc, so the dts is overall quite a bit smaller. I've believe I've got all aliases and the associated gianfar updates etc. that I'd somehow missed in the sbc8560 dts.

 powerpc/arch/powerpc/boot/dts/sbc8548.dts |  219 ++++++++++++++++++++++++++++++
 1 file changed, 219 insertions(+)

3) Add default .config file for Wind River SBC8548

This config gives basic serial console and ethernet support for doing an NFS root setup. The SBC8548 has one PCI-X slot, and a short PCI-e slot, so I've enabled PCI.

 powerpc/arch/powerpc/configs/sbc8548_defconfig |  740 +++++++++++++++++++++++++
 1 file changed, 740 insertions(+)

Like the 8560 board, I'd quickly spun together a u-boot 1.2.0 for testing this -- since that was the quickest route for me to get a powerpc capable version. This too needs a proper u-boot 1.3.1 patchset so we get all the associated updates within that, like local-mac-address etc. Soon...

Paul.