drm/sun4i: Implement A83T HDMI driver

A83T has DW HDMI IP block with a custom PHY similar to Synopsys gen2
HDMI PHY.

Only video output was tested, while HW also supports audio and CEC.
Support for them will be added later.

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/20180214200906.31509-11-jernej.skrabec@siol.net