pinctrl: sunxi: add support for H6 R_PIO pin controller

Allwinner H6 SoC has a R_PIO pin controller like other Allwinner SoCs,
which controls the PL and PM pin banks.

Add support for it.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>