platform: cznic: turris-omnia-mcu: Depend on OF

Add depend on OF, otherwise the compilation fails with
  error: no member named 'of_gpio_n_cells' in 'struct gpio_chip'
  error: no member named 'of_xlate' in 'struct gpio_chip'

Fixes: dfa556e4 ("platform: cznic: turris-omnia-mcu: Add support for MCU connected GPIOs")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202407031646.trNSwajF-lkp@intel.com/Signed-off-by: Marek Behún <kabel@kernel.org>
Link: https://lore.kernel.org/r/20240708114002.4285-2-kabel@kernel.orgSigned-off-by: Arnd Bergmann <arnd@arndb.de>

drivers/platform/cznic/Kconfig

@@ -16,6 +16,7 @@ config TURRIS_OMNIA_MCU
 	tristate "Turris Omnia MCU driver"
 	depends on MACH_ARMADA_38X || COMPILE_TEST
 	depends on I2C
+	depends on OF
 	select GPIOLIB
 	select GPIOLIB_IRQCHIP
 	select HW_RANDOM