iommu/amd: Refactor logic to program the host page table in DTE

iommu/amd: Refactor logic to program the host page table in DTE

Introduce the amd_iommu_set_dte_v1() helper function to configure
IOMMU host (v1) page table into DTE. This will be used later
when attaching nested doamin.

Also, remove obsolete warning when SNP is enabled and domain id
is zero since this check is no longer applicable.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>