dt-bindings: pinctrl: Add bindings for Awinic AW9523/AW9523B

Add bindings for the Awinic AW9523/AW9523B I2C GPIO Expander driver.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
Signed-off-by: David Bauer <mail@david-bauer.net>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210624214458.68716-1-mail@david-bauer.net


[Fixed up minor bugs found by new checking tools]
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>