tools: bpf: fix license for a compat header file

libc_compat.h is used by libbpf so make sure it's licensed under
LGPL or BSD license.  The license change should be OK, I'm the only
author of the file.
Signed-off-by: NJakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: NQuentin Monnet <quentin.monnet@netronome.com>
Acked-by: NYonghong Song <yhs@fb.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>

tools/include/tools/libc_compat.h

-// SPDX-License-Identifier: GPL-2.0+
+// SPDX-License-Identifier: (LGPL-2.0+ OR BSD-2-Clause)
 /* Copyright (C) 2018 Netronome Systems, Inc. */
 
 #ifndef __TOOLS_LIBC_COMPAT_H