dmaengine: don't run tests on rhel8
The iommu code it depends on is geared towards rhel9 and later currently. The iommu state check code needs to be changed before it can be used with rhel8. rhel8 defaulted to passthrough domains, so the code that configures the iommu needs to be changed to be explicit about whether iommu.passthrough is set or clear. Also avoid testing ptdma on 9.0, as the driver didn't exist then.
Edited by Jerry Snitselaar