ARM64: dts: odroid-c2: Add HDMI and CEC Nodes

Now the VPU Power Domain has been fixed while boothing from Mainline U-Boot,
VPU and HDMI nodes can finally be added to the Odroid-C2 DTS.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>