powerpc: FPGA support for GE Fanuc SBC610

Support for the SBC610 VPX Single Board Computer from GE Fanuc (PowerPC
MPC8641D).

This patch adds support for the registers held in the devices main FPGA,
exposing extra information about the revision of the board through cpuinfo.

Signed-off-by: Martyn Welch <martyn.welch@gefanuc.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>