cpu/x86/mtrr: Replace GPLv2 long form headers with SPDX header

Change-Id: I9d97cac214f04604f956cd9eee1e281b75c93645
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41134
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
diff --git a/src/cpu/x86/mtrr/mtrr.c b/src/cpu/x86/mtrr/mtrr.c
index 2698708..53b6400 100644
--- a/src/cpu/x86/mtrr/mtrr.c
+++ b/src/cpu/x86/mtrr/mtrr.c
@@ -1,15 +1,7 @@
 /* This file is part of the coreboot project. */
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
 /*
- *	This program is free software; you can redistribute it and/or modify
- *	it under the terms of the GNU General Public License as published by
- *	the Free Software Foundation; either version 2 of the License, or
- *	(at your option) any later version.
- *
- *	This program 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 General Public License for more details.
- *
  * mtrr.c: setting MTRR to decent values for cache initialization on P6
  * Derived from intel_set_mtrr in intel_subr.c and mtrr.c in linux kernel
  *