gpio: xilinx: use generic device properties

OF-specific routines should not be used unless necessary. Generic device
properties are preferred so switch to using them in the driver code.

Acked-by: Michal Simek <michal.simek@amd.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20240930144804.75068-3-brgl@bgdev.pl


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