src/superio: replace license boilerplate with SPDX

The authors from the header of the files are added in a previous commit.

Change-Id: Iafeaafb9689c65bd2f5de3960097ec0d4c1009e7
Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/38544
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/superio/smsc/sio1036/superio.c

@@ -1,17 +1,5 @@
-/*
- * This file is part of the coreboot project.
- *
- * Copyright (C) 2012 Advanced Micro Devices, Inc.
- *
- * 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; version 2 of the License.
- *
- * 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-only */
+/* This file is part of the coreboot project. */
 
 /* RAM driver for the SMSC SIO1036 Super I/O chip */