drm/amd/display: Add new DSC interface to disconnect from pipe

[Why & How]
Add new DSC interface to disconnect from pipe.

Reviewed-by: Alvin Lee <alvin.lee2@amd.com>
Acked-by: Wayne Lin <wayne.lin@amd.com>
Signed-off-by: Eric Bernstein <eric.bernstein@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>