gpio: raspberrypi-exp: use new GPIO line value setter callbacks

gpio: raspberrypi-exp: 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: Stefan Wahren <wahrenst@gmx.net>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://lore.kernel.org/r/20250614111216.93677-1-wahrenst@gmx.net
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>