dt-bindings: arm: airoha: Add binding for Airoha GPIO controller

Airoha's GPIO controller on their ARM EN7523 SoCs consists of two banks of 32
GPIOs

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: John Crispin <john@phrozen.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
[Bartosz: removed stray newline at the end of the file]
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>