util: Use SPDX headers

Change-Id: I2858fdf74e782f425d56653491cdebe83c185d19
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41208
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>

util/cbfstool/elf.h

@@ -1,17 +1,4 @@
-/* This file defines standard ELF types, structures, and macros.
-   Copyright (C) 1995-2003,2004,2005,2006,2007 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-*/
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
 
 #ifndef _ELF_H
 #define	_ELF_H 1