drm/amd/display: avoid link loss short pulse stuck the system

[Why]
MST monitor sends link loss short pulse continuous but sink is
occupy by HDMI input to lead link training fail.

[How]
disable link once retraining fail.
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Yu-ting Shen <yu-tshen@amd.com>
Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc_link.c

@@ -4279,6 +4279,8 @@ void core_link_enable_stream(
 			 */
 			if (status != DC_FAIL_DP_LINK_TRAINING ||
 					pipe_ctx->stream->signal == SIGNAL_TYPE_DISPLAY_PORT_MST) {
+				if (false == stream->link->link_status.link_active)
+					disable_link(stream->link, pipe_ctx->stream->signal);
 				BREAK_TO_DEBUGGER();
 				return;
 			}