arm64: allwinner: a64: add R_PIO pinctrl node

Allwinner A64 have a dedicated pin controller to manage the PL pin bank.
As the driver and the required clock support are added, add the device
node for it.

Signed-off-by: Icenowy Zheng <icenowy@aosc.xyz>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>