malta: arch/mips/include/asm/malta.h SPDX license tag

This patch replaces the GPL-2.0 text with a GPL-2.0
SPDX-License-Identifier tag, and adds Imagination Technologies copyright
following my recent changes.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>

arch/mips/include/asm/malta.h

 /*
  * Copyright (C) 2013 Gabor Juhos <juhosg@openwrt.org>
+ * Copyright (C) 2013 Imagination Technologies
  *
- * This program is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License version 2 as published
- * by the Free Software Foundation.
+ * SPDX-License-Identifier:	GPL-2.0
  */
 
 #ifndef _MIPS_ASM_MALTA_H