drivers: gpio: add driver for Microchip PIC32 GPIO controller.

drivers: gpio: add driver for Microchip PIC32 GPIO controller.

In PIC32 GPIO controller is part of PIC32 pin controller.
PIC32 has ten independently programmable ports and each with multiple pins.
Each of these pins can be configured and used as GPIO, provided they
are not in use for other peripherals.

Signed-off-by: Purna Chandra Mandal <purna.mandal@microchip.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>