gpio: fix up CONFIG_OF dependencies

gpio: fix up CONFIG_OF dependencies

A number of GPIO drivers that used to have a CONFIG_OF_GPIO dependency now fail
to build on targets without CONFIG_OF:

WARNING: unmet direct dependencies detected for GPIO_SYSCON
  Depends on [n]: GPIOLIB [=y] && HAS_IOMEM [=y] && MFD_SYSCON [=y] && OF [=n]
  Selected by [y]:
  - GPIO_SAMA5D2_PIOBU [=y] && GPIOLIB [=y] && HAS_IOMEM [=y] && MFD_SYSCON [=y] && (ARCH_AT91 || COMPILE_TEST [=y])

drivers/gpio/gpio-mt7621.c: In function 'mediatek_gpio_bank_probe':
drivers/gpio/gpio-mt7621.c:254:20: error: 'struct gpio_chip' has no member named 'of_gpio_n_cells'
  254 |         rg->chip.gc.of_gpio_n_cells = 2;
      |                    ^
drivers/gpio/gpio-tegra186.c: In function 'tegra186_gpio_of_xlate':
drivers/gpio/gpio-tegra186.c:502:25: error: 'struct gpio_chip' has no member named 'of_gpio_n_cells'
  502 |         if (WARN_ON(chip->of_gpio_n_cells < 2))
      |                         ^~
drivers/gpio/gpio-lpc32xx.c: In function 'lpc32xx_gpio_probe':
drivers/gpio/gpio-lpc32xx.c:523:49: error: 'struct gpio_chip' has no member named 'of_xlate'
  523 |                         lpc32xx_gpiochip[i].chip.of_xlate = lpc32xx_of_xlate;
      |                                                 ^
drivers/gpio/gpio-spacemit-k1.c: In function 'spacemit_gpio_add_bank':
drivers/gpio/gpio-spacemit-k1.c:234:11: error: 'struct gpio_chip' has no member named 'of_gpio_n_cells'
  234 |         gc->of_gpio_n_cells     = 3;
      |           ^~

Bring that back as a dependency.

Fixes: 7803501e5754 ("gpio: drop unneeded Kconfig dependencies on OF_GPIO")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://patch.msgid.link/20260325100144.1696731-1-arnd@kernel.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>