drm/amd/display: turn off eDP lcdvdd and backlight if not required

[why]
A+N configuration, eDP on A-APU is off, extended display active.
Resume from s4, eDP's backlight is still on.

[how]
Turn off inactive eDP backlight and lcdvdd.

Reviewed-by: Charlene Liu <charlene.liu@amd.com>
Reviewed-by: Aric Cyr <aric.cyr@amd.com>
Signed-off-by: Charlene Liu <Charlene.Liu@amd.com>
Signed-off-by: Jing Zhou <Jing.Zhou@amd.com>
Signed-off-by: Roman Li <roman.li@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

@@ -6298,10 +6298,10 @@ void dc_query_current_properties(struct dc *dc, struct dc_current_properties *pr
 void dc_set_edp_power(const struct dc *dc, struct dc_link *edp_link,
 				 bool powerOn)
 {
-	if (edp_link->connector_signal != SIGNAL_TYPE_EDP)
+	if (!edp_link || !edp_link->dc || !edp_link->dc->link_srv)
 		return;
 
-	if (edp_link->skip_implict_edp_power_control == false)
+	if (edp_link->connector_signal != SIGNAL_TYPE_EDP)
 		return;
 
 	edp_link->dc->link_srv->edp_set_panel_power(edp_link, powerOn);

drivers/gpu/drm/amd/display/dc/link/protocols/link_edp_panel_control.c

@@ -393,6 +393,7 @@ void edp_set_panel_power(struct dc_link *link, bool powerOn)
 
 		// 3. Rx power on
 		dpcd_write_rx_power_ctrl(link, true);
+		DC_LOG_BACKLIGHT("eDP power and backlight: Power on");
 	} else {
 		// 3. Rx power off
 		dpcd_write_rx_power_ctrl(link, false);
@@ -404,6 +405,7 @@ void edp_set_panel_power(struct dc_link *link, bool powerOn)
 		// 1. panel VDD off
 		if (!link->dc->config.edp_no_power_sequencing)
 			link->dc->hwss.edp_power_control(link, false);
+		DC_LOG_BACKLIGHT("eDP power and backlight: Power off");
 	}
 }