gpio: vx855: 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.

Link: https://lore.kernel.org/r/20250709-gpiochip-set-rv-gpio-remaining-v1-1-b8950f69618d@linaro.org


Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>