ARM: dts: sun8i-h3: Add R_PIO controller node to the dtsi

Add the corresponding device node for R_PIO on H3 to the dtsi. Support
for the controller was added in earlier commit.

Signed-off-by: Krzysztof Adamski <k@japko.eu>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>