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

The hardware address translation operations (ATOS) can be useful for
debugging.  arm-smmu used to have support for ATOS, but it was ripped
out while moving to the io-pgtable framework.  Resurrect the old ATOS
code with the following modifications:

  - Remove errata workarounds for deprecated hardware.
  - Move the atos lock to a spinlock (since the only reason a mutex was
    being used previously was due to the fact that some of the old
    errata workarounds required sleeping operations).

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