treewide: Convert more license headers to SPDX style

Change-Id: Ia3de79c7d71049da00ed108829eac6cb49ff3ed6
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41205
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

util/intelmetool/Makefile

@@ -1,14 +1,4 @@
-# intelmetool
-
-# 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.
+# SPDX-License-Identifier: GPL-2.0-or-later
 
 PROGRAM = intelmetool