powerpc: C2K board driver

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 3 of 5: driver for the board.  At this time it is very generic
and similar to its original, the driver for the prpmc2800.

Signed-off-by: Remi Machet <rmachet@slac.stanford.edu>
Signed-off-by: Paul Mackerras <paulus@samba.org>