ARM: dts: sun4i: Remove all useless pinctrl nodes

The gpio pinctrl nodes are redundant and as such useless most of the times.
Since they will also generate warnings in DTC, we can simply remove most of
them.

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