drm/amd/display: Don't compare same stream for synchronized vblank

[Why]
When determining synchronzied vblank we don't need to compare the stream
with itself

[How]
If comparing same stream, continue to next iteration
Signed-off-by: Alvin Lee <alvin.lee2@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@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/dcn20/dcn20_resource.c

@@ -2015,6 +2015,10 @@ int dcn20_populate_dml_pipes_from_context(
 			pipe_cnt = i;
 			continue;
 		}
+
+		if (res_ctx->pipe_ctx[pipe_cnt].stream == res_ctx->pipe_ctx[i].stream)
+			continue;
+
 		if (dc->debug.disable_timing_sync || !resource_are_streams_timing_synchronizable(
 				res_ctx->pipe_ctx[pipe_cnt].stream,
 				res_ctx->pipe_ctx[i].stream)) {