drm/amd/display: unit show garbage when do OPTC blank

[Why]
Unit enter to S4, garbage show on screen when do OPTC blank.

[How]
Wait for vblank then do OPTC blank
Signed-off-by: Paul Hsieh <paul.hsieh@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c

@@ -2581,8 +2581,10 @@ void dcn10_blank_pixel_data(
 		}
 	} else if (blank) {
 		dc->hwss.set_abm_immediate_disable(pipe_ctx);
-		if (stream_res->tg->funcs->set_blank)
+		if (stream_res->tg->funcs->set_blank) {
+			stream_res->tg->funcs->wait_for_state(stream_res->tg, CRTC_STATE_VBLANK);
 			stream_res->tg->funcs->set_blank(stream_res->tg, blank);
+		}
 	}
 }