drm/amd/display: Decrement refcount of dc_sink before reassignment

[why]
An old dc_sink state is causing a memory leak because it is missing a
dc_sink_release before a new dc_sink is assigned back to
aconnector->dc_sink.

[how]
Decrement the dc_sink refcount before reassigning it to a new dc_sink.
Signed-off-by: Victor Lu <victorchengchi.lu@amd.com>
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Acked-by: Anson Jacob <Anson.Jacob@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -2331,8 +2331,10 @@ void amdgpu_dm_update_connector_after_detect(
 		 * TODO: check if we still need the S3 mode update workaround.
 		 * If yes, put it here.
 		 */
-		if (aconnector->dc_sink)
+		if (aconnector->dc_sink) {
 			amdgpu_dm_update_freesync_caps(connector, NULL);
+			dc_sink_release(aconnector->dc_sink);
+		}
 
 		aconnector->dc_sink = sink;
 		dc_sink_retain(aconnector->dc_sink);