iommu/amd: Allow non-ATS devices in IOMMUv2 domains

With the grouping of multi-function devices a non-ATS
capable device might also end up in the same domain as an
IOMMUv2 capable device.
So handle this situation gracefully and don't consider it a
bug anymore.

Tested-by: Oded Gabbay <oded.gabbay@gmail.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>