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/common/hush.c b/common/hush.c
index cc81c9c..3f3a79c 100644
--- a/common/hush.c
+++ b/common/hush.c
@@ -71,20 +71,9 @@
  *      maybe change map[] to use 2-bit entries
  *      (eventually) remove all the printf's
  *
- * 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.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ * SPDX-License-Identifier:	GPL-2.0+
  */
+
 #define __U_BOOT__
 #ifdef __U_BOOT__
 #include <malloc.h>         /* malloc, free, realloc*/