gpio: nomadik: wrap a local variable in a necessary ifdef

The 'desc' local variable in nmk_gpio_dbg_show_one() is now only used
with CONFIG_PINCTRL_NOMADIK enabled so wrap its declaration with an
appropriate ifdef.

Fixes: ddeb66d2cb10 ("gpio: nomadik: don't print out global GPIO numbers in debugfs callbacks")
Reported-by: kernel test robot <[e-mail]>
Closes: https://lore.kernel.org/oe-kbuild-all/[e-mail]/
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Bartosz Golaszewski <[e-mail]>

drivers/gpio/gpio-nomadik.c

···
 			   struct gpio_chip *chip, unsigned int offset)
 {
 	struct nmk_gpio_chip *nmk_chip = gpiochip_get_data(chip);
+#ifdef CONFIG_PINCTRL_NOMADIK
 	struct gpio_desc *desc;
+#endif
 	int mode;
 	bool is_out;
 	bool data_out;