The next features we will need to share across drivers will need to
store some parameters for drivers to use, such as the selected output
format.
Let's create a new connector sub-state dedicated to HDMI controllers,
that will eventually store everything we need.
Reviewed-by: Dave Stevenson <dave.stevenson@xxxxxxxxxxxxxxx>
Signed-off-by: Maxime Ripard <mripard@xxxxxxxxxx>