sunxi: dts: H616: Enable the watchdog

For some reason, the watchdog was disabled in the H616 device tree. Most
likely this is a copy-paste from the H6 device tree: the H6 watchdog is
disabled because it is broken in some chips. However, there is no
evidence of issues with the H616 watchdog.

Enable the watchdog node so it can be used by the driver.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>