gpio: Add GPIO support for the ACCES 104-IDI-48

The ACCES 104-IDI-48 family of PC/104 utility boards feature 48
individually optically isolated digital inputs. Enabled inputs feature
change-of-state detection capability; if change-of-state detection is
enabled, an interrupt is fired off if a change of input level
(low-to-high or high-to-low) is detected. Change-of-state IRQs are
enabled/disabled on 8-bit boundaries, for a total of six boundaries.

This driver provides GPIO and IRQ support for these 48 channels of
digital input. The base port address for the device may be configured
via the idi_48_base module parameter. The interrupt line number for the
device may be configured via the idi_48_irq module parameter.

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