ARM: dove: Enable Dove watchdog in the devicetree

Add the devicetree node to enable watchdog support available in Dove SoCs.

Tested-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>