drm/amd/display: polling vid stream status in hpo dp blank

[why]
vid stream control is double bufferred, if we don't wait for video
stream enable set to 0, we may get temporary image corruption
showing on the stream when setting PIXEL_TO_SYMBOL_FIFO_ENABLE to 0.

Reviewed-by: Ariel Bernstein <Eric.Bernstein@amd.com>
Acked-by: Jasdeep Dhillon <jdhillon@amd.com>
Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>

drivers/gpu/drm/amd/display/dc/dcn31/dcn31_hpo_dp_stream_encoder.c

@@ -150,9 +150,9 @@ static void dcn31_hpo_dp_stream_enc_dp_blank(
 	 * 10us*5000=50ms. This covers 41.7ms of minimum 24 Hz mode +
 	 * a little more because we may not trust delay accuracy.
 	 */
-	//REG_WAIT(DP_SYM32_ENC_VID_STREAM_CONTROL,
-	//		VID_STREAM_STATUS, 0,
-	//		10, 5000);
+	REG_WAIT(DP_SYM32_ENC_VID_STREAM_CONTROL,
+			VID_STREAM_STATUS, 0,
+			10, 5000);
 
 	/* Disable SDP tranmission */
 	REG_UPDATE(DP_SYM32_ENC_SDP_CONTROL,