ssb: 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/20250610-gpiochip-set-rv-ssb-v1-1-0bee5b45b411@linaro.org


Signed-off-by: Johannes Berg <johannes.berg@intel.com>