iommu/arm-smmu: implement workaround for context fault hang errata

There is a hardware errata that could result in bus hang during context
fault processing.  The work around given by the hardware team is to
issue a TLBSYNC and terminate the transaction.  Implement the
workaround and provide a DT option to activate it.

Change-Id: Iede30ff68676188af1249fd2fd776bc84f224dc6
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>