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/drivers/net/phy/et1011c.c b/drivers/net/phy/et1011c.c
index 5e22399..70c15e2 100644
--- a/drivers/net/phy/et1011c.c
+++ b/drivers/net/phy/et1011c.c
@@ -4,16 +4,7 @@
  * Derived from Linux kernel driver by Chaithrika U S
  * Copyright (C) 2013, Texas Instruments, Incorporated - http://www.ti.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.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
+ * SPDX-License-Identifier:	GPL-2.0+
  */
 #include <config.h>
 #include <phy.h>