ARM: sunxi: Add a missing SPDX license header

Add the missing SPDX license header to arch/arm/mach-sunxi/platsmp.c.
Signed-off-by: Jason Wang <wangborong@cdjrlc.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20210810133138.109309-1-wangborong@cdjrlc.com

arch/arm/mach-sunxi/platsmp.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * SMP support for Allwinner SoCs
  *
@@ -8,9 +9,6 @@
  * Based on code
  *  Copyright (C) 2012-2013 Allwinner Ltd.
  *
- * This file is licensed under the terms of the GNU General Public
- * License version 2.  This program is licensed "as is" without any
- * warranty of any kind, whether express or implied.
  */
 
 #include <linux/delay.h>