drm/amd/display: change hw sequence

[Why]
t9 delay func is called twice after setting power off, the unexpected
action results in a doubling of the added 140ms t9 delay

[How]
If the backlight has been turned off, does not turn it off again

Signed-off-by: Sherry <[e-mail]>
Reviewed-by: Tony Cheng <[e-mail]>
Acked-by: Rodrigo Siqueira <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c

···
 		return;
 	}
 
-	if (enable && link->panel_cntl &&
-		link->panel_cntl->funcs->is_panel_backlight_on(link->panel_cntl)) {
-		DC_LOG_HW_RESUME_S3(
-				"%s: panel already powered up. Do nothing.\n",
+	if (link->panel_cntl) {
+		bool is_backlight_on = link->panel_cntl->funcs->is_panel_backlight_on(link->panel_cntl);
+
+		if ((enable && is_backlight_on) || (!enable && !is_backlight_on)) {
+			DC_LOG_HW_RESUME_S3(
+				"%s: panel already powered up/off. Do nothing.\n",
 				__func__);
-		return;
+			return;
+		}
 	}
 
 	/* Send VBIOS command to control eDP panel backlight */