Add support for multi-purpose pins (MPPs) on Qualcomm PM8xxx PMIC chips. PM8xxx MPPs can be configured as digital or analog inputs or outputs, current sinks, or buffers. Note that mpp pins appear as gpio lines to the kernel. However they are implemented separately from the pmic's gpio driver as mpps have different configuration attributes and have different register controls than the pmic's gpio controller. Basically they are different set of pins. Change-Id: Iab39b2f7c2ba3f35ef6ac74d37ee7add8c70681f Signed-off-by: David Collins <collinsd@codeaurora.org>