mfd: arizona: Allow GPIO to be specified for IRQ line

If a GPIO is specified for the chip IRQ line then request it. This
improves support for systems that do not put pins into input mode when
used as interrupts.

Also use this GPIO when the primary IRQ is in edge triggered mode to
detect if we have handled pending interrupts in order to improve
robustness.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>