mps2: Add defines and devices for FPGA system control block

These are fixed I/O registers for getting and setting the states of
LEDs, buttons, SPI chip-selects, and LCD control lines. It also contains
several free-running counters with no specific use.

Change-Id: Ib49306d5501574f7eb354165cdca6f29e3d4dad4
Signed-off-by: Jon Medhurst <tixy@linaro.org>