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

Add depend on WATCHDOG, otherwise modpost fails with
  ERROR: modpost: "watchdog_init_timeout" [drivers/platform/cznic/turris-omnia-mcu.ko] undefined!
  ERROR: modpost: "devm_watchdog_register_device" [drivers/platform/cznic/turris-omnia-mcu.ko] undefined!

Fixes: ab89fb5f ("platform: cznic: turris-omnia-mcu: Add support for MCU watchdog")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202407040711.g19y3cWq-lkp@intel.com/Signed-off-by: Marek Behún <kabel@kernel.org>
Link: https://lore.kernel.org/r/20240708114002.4285-3-kabel@kernel.orgSigned-off-by: Arnd Bergmann <arnd@arndb.de>

drivers/platform/cznic/Kconfig

@@ -17,6 +17,7 @@ config TURRIS_OMNIA_MCU
 	depends on MACH_ARMADA_38X || COMPILE_TEST
 	depends on I2C
 	depends on OF
+	depends on WATCHDOG
 	select GPIOLIB
 	select GPIOLIB_IRQCHIP
 	select HW_RANDOM