iommu/amd: Do not use IOMMUv2 functionality when SME is active

When memory encryption is active the device is likely not in a direct
mapped domain. Forbid using IOMMUv2 functionality for now until finer
grained checks for this have been implemented.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Link: https://lore.kernel.org/r/20200824105415.21000-3-joro@8bytes.org


Signed-off-by: Joerg Roedel <jroedel@suse.de>