drm/amd/display: support VSC SDP update on video test pattern request

[why]
MSA will be deprecated in the future.
Need to support VSC during DP test automation.

[how]
Do not disable VSC during DP test automation.
TODO - need to add VSC update on DM side on test request.

Signed-off-by: Wenjing Liu <Wenjing.Liu@amd.com>
Reviewed-by: Nikola Cornij <Nikola.Cornij@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>