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/freescale/common/ngpixis.h b/board/freescale/common/ngpixis.h
index a239ee3..364e749 100644
--- a/board/freescale/common/ngpixis.h
+++ b/board/freescale/common/ngpixis.h
@@ -2,10 +2,7 @@
  * Copyright 2010-2011 Freescale Semiconductor
  * Author: Timur Tabi <timur@freescale.com>
  *
- * 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+
  *
  * This file provides support for the ngPIXIS, a board-specific FPGA used on
  * some Freescale reference boards.