ANDROID: enable CONFIG_WATCHDOG_CORE=y

WATCHDOG was enabled, but we forgot about the watchdog core code, so
turn it on as well so that all vendors do not have to enable it in their
configs.

Reported-by: Orson Zhai <orsonzhai@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Iac14e304b15f774d52fb07aa65df86f3dd71797f