gpiolib: swnode: Make use of for_each_gpio_property_name()

For the sake of unification and easier maintenance replace
swnode_format_propname() call with for_each_gpio_property_name()
for-loop.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20240819142945.327808-5-andriy.shevchenko@linux.intel.com


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