dt-bindings: mfd: Add support for Airoha EN7581 GPIO System Controller

dt-bindings: mfd: Add support for Airoha EN7581 GPIO System Controller

Add support for Airoha EN7581 GPIO System Controller which provide a
register map for controlling the GPIO, pinctrl and PWM of the SoC via
dedicated pinctrl and pwm child nodes.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Co-developed-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://lore.kernel.org/20241023-en7581-pinctrl-v9-4-afb0cbcab0ec@kernel.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>