iommu/amd: Do not support IOMMUv2 APIs when SNP is enabled

The IOMMUv2 APIs (for supporting shared virtual memory with PASID)
configures the domain with IOMMU v2 page table, and sets DTE[Mode]=0.
This configuration cannot be supported on SNP-enabled system.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Link: https://lore.kernel.org/r/20220713225651.20758-10-suravee.suthikulpanit@amd.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>