serial: max310x: 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/r/20250408-gpiochip-set-rv-tty-v1-1-fb49444827d4@linaro.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>