arm64: dts: rockchip: enable rk3328 watchdog clock

Add the missing clock property for the watchdog on rk3328.

Signed-off-by: Leonidas P. Papadakos <papadakospan@gmail.com>
[set wdt node to always enabled, as it is not board-specific]
Signed-off-by: Heiko Stuebner <heiko@sntech.de>