Various Makefiles: Add SPDX-License-Identifier tags

After consulting with some of the SPDX team, the conclusion is that
Makefiles are worth adding SPDX-License-Identifier tags too, and most of
ours have one.  This adds tags to ones that lack them and converts a few
that had full (or in one case, very partial) license blobs into the
equivalent tag.

Cc: Kate Stewart <kstewart@linuxfoundation.org>
Signed-off-by: Tom Rini <trini@konsulko.com>

arch/powerpc/cpu/Makefile

@@ -1,3 +1,7 @@
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
 obj-$(CONFIG_MPC83xx) += mpc8xxx/
 obj-$(CONFIG_MPC85xx) += mpc8xxx/
 obj-$(CONFIG_MPC86xx) += mpc8xxx/

arch/powerpc/cpu/mpc8xxx/Makefile

@@ -1,9 +1,7 @@
 #
 # Copyright 2009-2010 Freescale Semiconductor, Inc.
 #
-# This program is free software; you can redistribute it and/or
-# modify it under the terms of the GNU General Public License
-# Version 2 as published by the Free Software Foundation.
+# SPDX-License-Identifier:	GPL-2.0
 #
 
 MINIMAL=