pinctrl: at91-pio4: use new GPIO line value setter callbacks

pinctrl: at91-pio4: 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>
Reviewed-by: Claudiu Beznea <claudiu.beznea@tuxon.dev>
Link: https://lore.kernel.org/20250408-gpiochip-set-rv-pinctrl-part1-v1-1-c9d521d7c8c7@linaro.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>