iommu/arm-smmu: remove potential NULL dereference on mapping path

When handling mapping requests, we dereference the SMMU domain before
checking that it is NULL. This patch fixes the issue by removing the check
altogether, since we don't actually use the leaf_smmu when creating
mappings.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index 6dbcaa4..ef77e3d 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -1423,9 +1423,8 @@
 			phys_addr_t paddr, size_t size, int flags)
 {
 	struct arm_smmu_domain *smmu_domain = domain->priv;
-	struct arm_smmu_device *smmu = smmu_domain->leaf_smmu;
 
-	if (!smmu_domain || !smmu)
+	if (!smmu_domain)
 		return -ENODEV;
 
 	/* Check for silent address truncation up the SMMU chain. */