[POWERPC] 86xx: Add defconfig for Wind River SBC8641D board

This adds a sample defconfig for the Wind River SBC8641D
board, with SMP, PCI and NFS root enabled.

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