hwmon: (ltc2992) Use new GPIO line value setter callbacks

hwmon: (ltc2992) 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/20250407-gpiochip-set-rv-hwmon-v1-1-1fa38f34dc07@linaro.org
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
[groeck: Fixed multi-line alignment issue]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>