add pragma once and copyright info

Signed-off-by: Drew Lewis <[email protected]>

Author: calewis

src/utl/include/utl/SuppressStdout.h

@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-3-Clause
+// Copyright (c) 2025, The OpenROAD Authors
+
+#pragma once
+
 #include "utl/Logger.h"
 
 namespace utl {