drm/amd/display: Connect DIG FE to its BE before link training starts

[why]
In SST mode no idle pattern will be generated after link training if
DIG FE is not connected to DIG BE.
Signed-off-by: Nikola Cornij <nikola.cornij@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -1546,6 +1546,10 @@ static enum dc_status enable_link_dp(
 	panel_mode = dp_get_panel_mode(link);
 	dp_set_panel_mode(link, panel_mode);
 
+	/* We need to do this before the link training to ensure the idle pattern in SST
+	 * mode will be sent right after the link training */
+	link->link_enc->funcs->connect_dig_be_to_fe(link->link_enc,
+						    pipe_ctx->stream_res.stream_enc->id, true);
 	skip_video_pattern = true;
 
 	if (link_settings.link_rate == LINK_RATE_LOW)