powerpc/QE: implement support for the GPIO LIB API

This is needed to access QE GPIOs via Linux GPIO API.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Acked-By: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>