pincntrl: add support for ams AS3722 pin control driver

The AS3722 is a compact system PMU suitable for mobile phones, tablets etc.

Add a driver to support accessing the GPIO, pinmux and pin configuration
of 8 GPIO pins found on the ams AS3722 through pin control driver and
gpiolib.

The driver will register itself as the pincontrol driver and gpio driver.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>