gpio: Add GPIO support for the Diamond Systems GPIO-MM

The Diamond Systems GPIO-MM device features 48 lines of digital I/O via
the emulation of dual 82C55A PPI chips. This driver provides GPIO
support for these 48 channels of digital I/O. The base port addresses
for the devices may be configured via the base array module parameter.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>