drm/amd/display: Read USB4 DP tunneling data from DPCD.

[Why]
We requires information from DPCD in order to identify USB4 DP
tunneling targets.

[How]
Add USB4 DP tunneling fields to DPCD struct and populate these fields
during sink detection.

Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Wayne Lin <Wayne.Lin@amd.com>
Acked-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Jimmy Kizito <Jimmy.Kizito@amd.com>