gpiolib: Introduce for_each_gpio_property_name() helper

Introduce a helper macro for_each_gpio_property_name().
With that in place, update users. This, in particular,
will help making the following simplifications easier.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20240819142945.327808-2-andriy.shevchenko@linux.intel.com


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