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>
diff --git a/board/compal/paz00/Makefile b/board/compal/paz00/Makefile
index b5fde8d..aa56643 100644
--- a/board/compal/paz00/Makefile
+++ b/board/compal/paz00/Makefile
@@ -4,14 +4,7 @@
 # See file CREDITS for list of people who contributed to this
 # project.
 #
-# This program is free software; you can redistribute it and/or modify it
-# under the terms and conditions of the GNU General Public License,
-# version 2, as published by the Free Software Foundation.
-#
-# This program is distributed in the hope 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
 #
 
 obj-y	:= paz00.o