Add GPL-2.0+ SPDX-License-Identifier to source files

Signed-off-by: Wolfgang Denk <wd@denx.de>
[trini: Fixup common/cmd_io.c]
Signed-off-by: Tom Rini <trini@ti.com>
diff --git a/board/ifm/o2dnt2/Makefile b/board/ifm/o2dnt2/Makefile
index e05b9c1..1dd3fe9 100644
--- a/board/ifm/o2dnt2/Makefile
+++ b/board/ifm/o2dnt2/Makefile
@@ -2,13 +2,7 @@
 # (C) Copyright 2005-2006
 # Wolfgang Denk, DENX Software Engineering, wd@denx.de.
 #
-# 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 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.
+# SPDX-License-Identifier:	GPL-2.0+
 #
 
 include $(TOPDIR)/config.mk