malta: fix missing watchdog core dependency for hwmon-sch5627

Fixes following error uncovered while building malta/be on 5.4:

 Package kmod-hwmon-sch5627 is missing dependencies for the following libraries:
 watchdog.ko

That dependency was introduced in upstream via 2d8c7ff52c24
("hwmon/sch56xx: Depend on watchdog for watchdog core functions") in
v3.5.

The issue emerged in 5.4 because the kconfig symbol CONFIG_WATCHDOG_CORE
is now a tristate value.  Previously it was a bool

Cc: Yousong Zhou <yszhou4tech@gmail.com>
Signed-off-by: Petr Štetiar <ynezz@true.cz>
Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>
(drop the config-4.19 change.  reword about the cause)

target/linux/malta/config-5.4

@@ -341,4 +341,5 @@ CONFIG_VT=y
 CONFIG_VT_CONSOLE=y
 CONFIG_VT_HW_CONSOLE_BINDING=y
 CONFIG_VXFS_FS=y
+CONFIG_WATCHDOG_CORE=y
 CONFIG_XPS=y