ARM: sunxi: dt: declare the r_pio pin controller for A31 SoC

The A31 SoC has a different pin controller for PL and PM banks.
Define this new controller in the device tree.

Signed-off-by: Boris BREZILLON <boris.brezillon@free-electrons.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>