[POWERPC] 85xx: Add default .config file for Wind River SBC8560

This is a suitable .config file for building the WRS SBC8560 kernel
to be used for NFS root via one of the TSEC interfaces and with
serial console via the 16550 compatible UART on the board.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>