pinctrl: sunxi: Add A23 R_PIO controller support

The A23 has a R_PIO pin controller, similar to the one found on the A31 SoC.
Add support for the pins controlled by the R_PIO controller.

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>