gpio: Add IRQ support to ACCES 104-IDIO-16 driver

gpio: Add IRQ support to ACCES 104-IDIO-16 driver

The ACCES 104-IDIO-16 series offers Change-of-State detection interrupt
functionality; if Change-of-State detection is enabled, an interrupt is
fired off if any input line changes state (i.e. goes from low to high,
or from high to low). This patch adds support to handle these interrupts
and allows the user to mask which GPIO lines are affected. The interrupt
line number for the device may be set via the idio_16_irq module
parameter.

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