gpiolib: wrap gpio_chip::set()

We have three places where we dereference the gpio_chip::set() callback.
In order to make it easier to incorporate the upcoming new variant of
this callback (one returning an integer value), wrap it in a helper so
that the dereferencing only happens once.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Link: https://lore.kernel.org/r/20250220-gpio-set-retval-v2-3-bc4cfd38dae3@linaro.org


Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>