net: dsa: vsc73xx: 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://patch.msgid.link/20250616-gpiochip-set-rv-net-v2-1-cae0b182a552@linaro.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>