arm64: dts: mt8173-evb: enable HDMI output

Add an HDMI connector node and enable the devices that are part of the
HDMI display path: cec, dpi0, hdmi_phy, and hdmi0.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>