iommu/arm-smmu: Implement hardware iova-to-phys

The hardware address translation operations (ATOS) can be useful for
debugging; however hardware may have limitations which prevent useage
of this functionality under all scenarios.

In the particular case of qcom,smmu-v2, halting the client is required
during atos. Additionally, nonatomic clock/regulator operations must
be performed.

Change-Id: I1a021026b9ee41ba2c1761bd5d5b7a13399c6417
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>