gpio: Add support for Airoha EN7523 GPIO controller

Airoha's GPIO controller on their ARM EN7523 SoCs consists of two banks of 32
GPIOs. Each instance in DT is for a single bank.

Acked-by: Bartosz Golaszewski <brgl@bgdev.pl>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: John Crispin <john@phrozen.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>