ARM: dts: sunxi: Rename gpio pinctrl names

We've had a pinctrl node name convention for a while now, let's follow
it for the AXP pinctrl nodes as well.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Link: https://lore.kernel.org/r/20210901091852.479202-41-maxime@cerno.tech