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.

Change-Id: I47dd61f68e8322e5716b82eecf20f1ceb2b94964
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Git-commit: 5552ecdbf9fb4f7608c1d7933a8baafcfa1bb337
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>