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/include/ks8721.h b/include/ks8721.h
index 185d9bd..90ed178 100644
--- a/include/ks8721.h
+++ b/include/ks8721.h
@@ -5,10 +5,7 @@
  *
  * Authors:	Eric Benard (based on dm9161.h)
  *
- *		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+
  */
 
 /* MICREL PHYSICAL LAYER TRANSCEIVER KS8721 */