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/matrix_vision/mergerbox/mergerbox.h b/board/matrix_vision/mergerbox/mergerbox.h
index d666d07..53eab28 100644
--- a/board/matrix_vision/mergerbox/mergerbox.h
+++ b/board/matrix_vision/mergerbox/mergerbox.h
@@ -2,13 +2,7 @@
  * Copyright (C) 2011 Matrix Vision GmbH
  * Andre Schwarz <andre.schwarz@matrix-vision.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+
  */
 
 #ifndef __MERGERBOX_H__