dt-bindings: display: sun4i-drm: Add A83T HDMI pipeline

This commit adds all necessary compatibles and descriptions needed to
implement A83T HDMI pipeline.

Mixer is already properly described, so only compatible is added.

However, A83T TV TCON, which is connected to HDMI, doesn't have channel 0,
contrary to all TCONs currently described. Because of that, TCON
documentation is extended.

A83T features Synopsys DW HDMI controller with a custom PHY which looks
like Synopsys Gen2 PHY with few additions. Since there is no
documentation, needed properties were found out through experimentation
and reading BSP code.

At the end, example is added for newer SoCs, which feature DE2 and DW
HDMI.

Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180214200906.31509-7-jernej.skrabec@siol.net