armvirt: fix missing watchdog core dependency for hwmon-sch5627

Fixes following error uncovered while building armvirt/64 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.

Signed-off-by: Petr Štetiar <ynezz@true.cz>

target/linux/armvirt/config-5.4

@@ -240,4 +240,5 @@ CONFIG_VIRTIO_MMIO=y
 CONFIG_VIRTIO_NET=y
 CONFIG_VIRTIO_PCI=y
 CONFIG_VIRTIO_PCI_LEGACY=y
+CONFIG_WATCHDOG_CORE=y
 CONFIG_XPS=y