iommu/arm-smmu-v3: Add SPDX header

Replace license text with SDPX header
Signed-off-by: Andrew Murray <andrew.murray@arm.com>
Acked-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/arm-smmu-v3.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * IOMMU API for ARM architected SMMUv3 implementations.
  *
- * 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.
- *
- * 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, see <http://www.gnu.org/licenses/>.
- *
  * Copyright (C) 2015 ARM Limited
  *
  * Author: Will Deacon <will.deacon@arm.com>