gpiolib: deprecate gpio_chip::set and gpio_chip::set_multiple

We now have setter callbacks that allow us to indicate success or
failure using the integer return value. Deprecate the older callbacks so
that no new code is tempted to use them.

Link: https://lore.kernel.org/r/20250227083748.22400-1-brgl@bgdev.pl


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