iommu/arm-smmu: Pass external fault information to client handlers

A client fault handler flag was recently introduced to indicate external
faults.  Use it.

Change-Id: Ib9ea59befc3c8324de4fc94a0dbe4acafaa6f9b8
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>