Makefile: Use SPDX identifier

Change-Id: Ia05f2ecd31d0606dfe2bca843dbe6df2b8212a27
Signed-off-by: Jacob Garber <jgarber1@ualberta.ca>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41598
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/LICENSES/retained-copyrights.txt b/LICENSES/retained-copyrights.txt
index 6775d2e..671f37f 100644
--- a/LICENSES/retained-copyrights.txt
+++ b/LICENSES/retained-copyrights.txt
@@ -25,6 +25,8 @@
 Copyright (C) 2008 Advanced Micro Devices, Inc.
 Copyright (c) 2008, Google Inc.
 Copyright (C) 2008 Jordan Crouse <jordan@cosmicpenguin.net>
+Copyright (C) 2008 Uwe Hermann <uwe@hermann-uwe.de>
+Copyright (C) 2009-2010 coresystems GmbH
 Copyright (c) 2009-2012, Code Aurora Forum. All rights reserved.
 Copyright (c) 2010-2017, The Regents of the University of California
 Copyright (c) 2010, Code Aurora Forum. All rights reserved.
@@ -36,6 +38,7 @@
 Copyright (c) 2011 - 2014 The Linux Foundation. All rights reserved.
 Copyright (c) 2011-2019 The Linux Foundation. All rights reserved.
 Copyright (c) 2011, Google Inc.
+Copyright (C) 2011 secunet Security Networks AG
 Copyright (c) 2012 - 2013, 2015, 2019 The Linux Foundation.
 Copyright (c) 2012 - 2013, 2015 The Linux Foundation. All rights reserved.
 Copyright (c) 2012 - 2013 The Linux Foundation. All rights reserved.
diff --git a/Makefile b/Makefile
index 470be94..2bc2a6f 100644
--- a/Makefile
+++ b/Makefile
@@ -1,33 +1,4 @@
-##
-##
-## Copyright (C) 2008 Advanced Micro Devices, Inc.
-## Copyright (C) 2008 Uwe Hermann <uwe@hermann-uwe.de>
-## Copyright (C) 2009-2010 coresystems GmbH
-## Copyright (C) 2011 secunet Security Networks AG
-##
-## Redistribution and use in source and binary forms, with or without
-## modification, are permitted provided that the following conditions
-## are met:
-## 1. Redistributions of source code must retain the above copyright
-##    notice, this list of conditions and the following disclaimer.
-## 2. Redistributions in binary form must reproduce the above copyright
-##    notice, this list of conditions and the following disclaimer in the
-##    documentation and/or other materials provided with the distribution.
-## 3. The name of the author may not be used to endorse or promote products
-##    derived from this software without specific prior written permission.
-##
-## THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
-## ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
-## IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
-## ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
-## FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
-## DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
-## OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
-## HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
-## LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
-## OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
-## SUCH DAMAGE.
-##
+## SPDX-License-Identifier: BSD-3-Clause
 
 ifneq ($(words $(CURDIR)),1)
     $(error Error: Path to the main directory cannot contain spaces)