This patch is adding support for generating memory requests which set the StreamID/SubstreamID field, so that is possible to emulate devices attached to an external IOMMU/SMMU with a Traffic generator. Change-Id: Iea068de581ae7125a9d49314124a08c045c75b49 Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com> Reviewed-on: https://gem5-review.googlesource.com/12188