pinctrl: sunxi: use gpiolib API to mark a GPIO used as an IRQ

When an IRQ is started on a GPIO line, mark this GPIO as IRQ in
the gpiolib so we can keep track of the usage centrally.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>