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/gpio.h b/arch/arm/include/asm/arch-at91/gpio.h
index 293d0bf..0700427 100644
--- a/arch/arm/include/asm/arch-at91/gpio.h
+++ b/arch/arm/include/asm/arch-at91/gpio.h
@@ -3,11 +3,7 @@
  *
  *  Copyright (C) 2005 HP Labs
  *
- * 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 __ASM_ARCH_AT91_GPIO_H