arm64: dts: rockchip: Enable nanopi4 HDMI audio

All the nanopi4 boards have HDMI, so let them make noise on it.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/7fe6e94e4b9f5986f19f2637b7b716f0cb54de1b.1570444701.git.robin.murphy@arm.com


Signed-off-by: Heiko Stuebner <heiko@sntech.de>