[POWERPC] 85xx: Add v1 device tree source for Wind River SBC8548 board

This adds a v1 device tree source for the Wind River SBC8548 board.
The biggest difference between this and the MPC8548CDS reference
platform is the absence of the CDS's Arcadia peripherals and physical
access to the PCI#2 bus.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>