iommu: arm-smmu: Add qsmmuv500 ECATS support

ECATS is a debug system similar to the optional ATOS operation described
by the ARM iommu specification. ECATS is only supported on the qsmmuv500
platform.

Change-Id: I5204b0b7a2db636ed9301bb09ad59f42a95ad200
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>