gpio: xilinx: use helper variable to store the address of pdev->dev

For better readability don't repeatedly dereference pdev->dev but
instead store the address of the embedded struct device in a local
variable in probe().

Acked-by: Michal Simek <michal.simek@amd.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20240930144804.75068-2-brgl@bgdev.pl


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