platform: cznic: turris-omnia-mcu: fix Kconfig dependencies

The newly added driver causes a Kconfig warning:

WARNING: unmet direct dependencies detected for RTC_CLASS
  Depends on [n]: !S390 [=y]
  Selected by [m]:
  - TURRIS_OMNIA_MCU [=m] && CZNIC_PLATFORMS [=y] && (MACH_ARMADA_38X || COMPILE_TEST [=y]) && I2C [=m] && OF [=y] && WATCHDOG [=y]

The problem here is that it selects entire subsystems, which normal
device drivers should not do. Changes all of these to 'depends on'
instead.

Fixes: dfa556e4 ("platform: cznic: turris-omnia-mcu: Add support for MCU connected GPIOs")
Fixes: 90e700fd ("platform: cznic: turris-omnia-mcu: Add support for poweroff and wakeup")
Fixes: ab89fb5f ("platform: cznic: turris-omnia-mcu: Add support for MCU watchdog")
Fixes: 41bb142a ("platform: cznic: turris-omnia-mcu: Add support for MCU provided TRNG")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

drivers/platform/cznic/Kconfig

@@ -18,11 +18,11 @@ config TURRIS_OMNIA_MCU
 	depends on I2C
 	depends on OF
 	depends on WATCHDOG
-	select GPIOLIB
+	depends on GPIOLIB
+	depends on HW_RANDOM
+	depends on RTC_CLASS
+	depends on WATCHDOG_CORE
 	select GPIOLIB_IRQCHIP
-	select HW_RANDOM
-	select RTC_CLASS
-	select WATCHDOG_CORE
 	help
 	  Say Y here to add support for the features implemented by the
 	  microcontroller on the CZ.NIC's Turris Omnia SOHO router.