pinctrl: Convert Allwinner Pin Controller to a schema

pinctrl: Convert Allwinner Pin Controller to a schema

The Allwinner SoCs have a pin controller supported in Linux, with a
matching Device Tree binding.

Now that we have the DT validation in place, let's convert the device tree
bindings for that controller over to a YAML schemas.

Signed-off-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/20191022160806.42971-1-mripard@kernel.org
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>