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/arch/arm/include/asm/arch-at91/at91_shdwn.h b/arch/arm/include/asm/arch-at91/at91_shdwn.h
index 874f988..18d9ea6 100644
--- a/arch/arm/include/asm/arch-at91/at91_shdwn.h
+++ b/arch/arm/include/asm/arch-at91/at91_shdwn.h
@@ -5,10 +5,7 @@
  * Shutdown Controller
  * Based on AT91SAM9XE datasheet
  *
- * 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+
  */
 
 #ifndef AT91_SHDWN_H