drm/amd/display: disable seamless boot for external DP

[Why]
Primary feature use case is with eDP panels.

[How]
Fail seamless boot validation if display is not an eDP panel.
Signed-off-by: Anthony Wang <anthony1.wang@amd.com>
Reviewed-by: Martin Leung <Martin.Leung@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@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.c

@@ -1323,11 +1323,10 @@ bool dc_validate_seamless_boot_timing(const struct dc *dc,
 	struct dc_link *link = sink->link;
 	unsigned int i, enc_inst, tg_inst = 0;
 
-	// Seamless port only support single DP and EDP so far
-	if ((sink->sink_signal != SIGNAL_TYPE_DISPLAY_PORT &&
-		sink->sink_signal != SIGNAL_TYPE_EDP) ||
-		sink->sink_signal == SIGNAL_TYPE_DISPLAY_PORT_MST)
+	/* Support seamless boot on EDP displays only */
+	if (sink->sink_signal != SIGNAL_TYPE_EDP) {
 		return false;
+	}
 
 	/* Check for enabled DIG to identify enabled display */
 	if (!link->link_enc->funcs->is_dig_enabled(link->link_enc))