gpiolib: Revert "Don't WARN on gpiod_put() for optional GPIO"

gpiolib: Revert "Don't WARN on gpiod_put() for optional GPIO"

No need to double check the pointer for NULL since gpiod_free()
is using VALIDATE_DESC_VOID() which simply returns in that case.

This reverts commit 1d7765ba15aca68f3bc52f59434c1c34855bbb54.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20250416095645.2027695-5-andriy.shevchenko@linux.intel.com
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>