arm: allwinner: Add GPIO Interrupt support

Not all pins in Allwinner have interrupts support so we rely
on the padconf data to add the proper caps when pin_getcaps is called.
The pin is switch to the specific "eint" function during setup_intr and
switched back to its old function in teardown_intr.
Only INTR_MAP_DATA_GPIO is supported for now.

MFC after: 1 month