gpio: loongson: use new line value setter callbacks

gpio: loongson: use new 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.

Reviewed-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20250423-gpiochip-set-rv-gpio-part2-v1-11-b22245cde81a@linaro.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>