[Why]
For userspace to send static HDR metadata to the display we need to
attach the property on the connector and send it to DC.

[How]
The property is attached to HDMI and DP connectors. Since the metadata
isn't actually available when creating the connector this isn't a
property we can dynamically support based on the extension block
being available or not.

When the HDR metadata is changed a modeset will be forced for now.
We need to switch from 8bpc to 10bpc in most cases anyway, and we want
to fully exit HDR mode when userspace gives us a NULL metadata, so this
isn't completely unnecessary.

The requirement can later be reduced to just entering and exiting HDR
or switching max bpc.

Cc: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190528190836.10738-2-nicholas.kazlauskas@amd.com