mfd: add ASIC3_CONFIG_GPIO templates

As ASIC3 GPIO alternate function configuration is expected to be similar
for several devices, it is convenient to define descriptive macros. This
patch is inspired by the PXA MFP configuration, the alternate functions
were observed on hx4700 and blueangel.

Signed-off-by: Philipp Zabel <philipp.zabel@gmail.com>
Signed-off-by: Samuel Ortiz <sameo@openedhand.com>