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/bootcount/bootcount_ram.c b/drivers/bootcount/bootcount_ram.c
index 8655af7..5bdabcd 100644
--- a/drivers/bootcount/bootcount_ram.c
+++ b/drivers/bootcount/bootcount_ram.c
@@ -2,19 +2,7 @@
  * (C) Copyright 2010
  * Heiko Schocher, DENX Software Engineering, hs@denx.de.
  *
- * See file CREDITS for list of people who contributed to this
- * project.
- *
- * 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 <common.h>