powerpc: Default configuration for C2K

Support for the C2K cPCI Single Board Computer from GEFanuc
(PowerPC MPC7448 with a Marvell MV64460 chipset).
All features of the board are not supported yet, but the board
boots, flash works, all Ethernet ports are working and PCI
devices are all found (USB and SATA on PCI1 do not work yet).

Part 4 of 5: this is the default config for the board.  In this
configuration the kernel is going to try to boot from MTD
partition 3 on the NOR flash (see c2k.dts for details about
the partitioning of the flash).
Signed-off-by: Remi Machet <rmachet@slac.stanford.edu>
Signed-off-by: Paul Mackerras <paulus@samba.org>