iommu/arm-smmu: Constify iommu_gather_ops structures

Check for iommu_gather_ops structures that are only stored in the tlb
field of an io_pgtable_cfg structure. The tlb field is of type
const struct iommu_gather_ops *, so iommu_gather_ops structures
having this property can be declared as const.
Acked-by: NJulia Lawall <julia.lawall@lip6.fr>
Signed-off-by: NBhumika Goyal <bhumirks@gmail.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>

drivers/iommu/arm-smmu-v3.c

@@ -1358,7 +1358,7 @@ static void arm_smmu_tlb_inv_range_nosync(unsigned long iova, size_t size,
 	} while (size -= granule);
 }
 
-static struct iommu_gather_ops arm_smmu_gather_ops = {
+static const struct iommu_gather_ops arm_smmu_gather_ops = {
 	.tlb_flush_all	= arm_smmu_tlb_inv_context,
 	.tlb_add_flush	= arm_smmu_tlb_inv_range_nosync,
 	.tlb_sync	= arm_smmu_tlb_sync,