watchdog: max77620_wdt: fix potential build errors

max77620_wdt uses watchdog core functions. Enable CONFIG_WATCHDOG_CORE
to fix potential build errors.
Signed-off-by: David Engraf <david.engraf@sysgo.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20191127084617.16937-1-david.engraf@sysgo.comSigned-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

drivers/watchdog/Kconfig

@@ -687,6 +687,7 @@ config MAX63XX_WATCHDOG
 config MAX77620_WATCHDOG
 	tristate "Maxim Max77620 Watchdog Timer"
 	depends on MFD_MAX77620 || COMPILE_TEST
+	select WATCHDOG_CORE
 	help
 	 This is the driver for the Max77620 watchdog timer.
 	 Say 'Y' here to enable the watchdog timer support for