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>

include/dm9000.h

@@ -3,10 +3,7 @@
  *
  * Authors:     Remy Bohmer <linux@bohmer.net>
  *
- *              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 __DM9000_H__
 #define __DM9000_H__