ARM: virtualization: replace verbose license with SPDX identifier

The original creation of arch/arm/cpu/armv7/{virt-v7.c,nonsec_virt.S}
predates the SPDX conversion, so the original elaborate license
statements sneaked in.
Fix this by replacing them with the proper abbreviation.

Signed-off-by: Andre Przywara <andre.przywara@linaro.org>
diff --git a/arch/arm/cpu/armv7/nonsec_virt.S b/arch/arm/cpu/armv7/nonsec_virt.S
index 358348f..24b4c18 100644
--- a/arch/arm/cpu/armv7/nonsec_virt.S
+++ b/arch/arm/cpu/armv7/nonsec_virt.S
@@ -3,23 +3,7 @@
  *
  * Copyright (c) 2013	Andre Przywara <andre.przywara@linaro.org>
  *
- * See file CREDITS for list of people who contributed to this
- * project.
- *
- * 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.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
- * MA 02111-1307 USA
+ * SPDX-License-Identifier:	GPL-2.0+
  */
 
 #include <config.h>