iommu/iommu-debug: Add functional test for ARM DMA IOMMU mapper

The vanilla ARM DMA IOMMU mapper is used by many clients in our system,
but we have no functional test coverage of it.  Add some functional
testing for it by leveraging the tests that were recently added for the
Fast DMA mapper.  Since the Fast mapper and the ARM mapper are both DMA
API implementations we can share most of the code.

CRs-Fixed: 997751
Change-Id: I58734a82f4dc3e4658ab7995b6682205097da991
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>