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/board/renesas/rsk7269/lowlevel_init.S b/board/renesas/rsk7269/lowlevel_init.S
index 399beb8..a2b174b 100644
--- a/board/renesas/rsk7269/lowlevel_init.S
+++ b/board/renesas/rsk7269/lowlevel_init.S
@@ -6,8 +6,7 @@
  *
  * Based on board/renesas/rsk7264/lowlevel_init.S
  *
- * This file is released under the terms of GPL v2 and any later version.
- * See the file COPYING in the root directory of the source tree for details.
+ * SPDX-License-Identifier:	GPL-2.0+
  */
 #include <config.h>
 #include <version.h>