drm: bridge: analogix/dp: add panel prepare/unprepare in suspend/resume time

Turn off the panel power in suspend time would help to reduce
power waste.

Tested-by: Caesar Wang <wxt@rock-chips.com>
Tested-by: Douglas Anderson <dianders@chromium.org>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Yakir Yang <ykk@rock-chips.com>

drivers/gpu/drm/bridge/analogix/analogix_dp_core.c

@@ -1400,6 +1400,12 @@ int analogix_dp_suspend(struct device *dev)
 	struct analogix_dp_device *dp = dev_get_drvdata(dev);
 
 	clk_disable_unprepare(dp->clock);
+
+	if (dp->plat_data->panel) {
+		if (drm_panel_unprepare(dp->plat_data->panel))
+			DRM_ERROR("failed to turnoff the panel\n");
+	}
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(analogix_dp_suspend);
@@ -1415,6 +1421,13 @@ int analogix_dp_resume(struct device *dev)
 		return ret;
 	}
 
+	if (dp->plat_data->panel) {
+		if (drm_panel_prepare(dp->plat_data->panel)) {
+			DRM_ERROR("failed to setup the panel\n");
+			return -EBUSY;
+		}
+	}
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(analogix_dp_resume);