iommu/arm-smmu: prefer stage-1 mappings where we have a choice

For an SMMU that supports both Stage-1 and Stage-2 mappings (but not
nested translation), then we should prefer stage-1 mappings as we
otherwise rely on the memory attributes of the incoming transactions
for IOMMU_CACHE mappings.

Change-Id: Ic2b885c55dabe1af7efde2ffc70690d0e2d1bf34
Signed-off-by: Will Deacon <will.deacon@arm.com>
Git-commit: 9c5c92e35cf5c4f7ee523d62a6bf9d5dc290350b
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git


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