pinctrl: sunxi: Add A64 R_PIO controller support

The A64 has a R_PIO pin controller, similar to the one found on the H3 SoC.
Add support for the pins controlled by the R_PIO controller.

Signed-off-by: Icenowy Zheng <icenowy@aosc.xyz>
Acked-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>