pinctrl: mediatek: common: use new GPIO line value setter callbacks

struct gpio_chip now has callbacks for setting line values that return
an integer, allowing to indicate failures. Convert the driver to using
them.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Link: https://lore.kernel.org/20250425-gpiochip-set-rv-pinctrl-mediatek-v1-5-93e6a01855e7@linaro.org


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>