ARM: dts: sun9i: Remove GPIO pinctrl nodes to avoid warnings

The A80 boards still define some GPIO pinctrl nodes that are not really
useful, and redundant with the muxing already happening on gpio_request.

Let's remove those nodes. This will also remove DTC warnings.

Acked-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>