iommu/amd: Do not set amd_iommu_pgtable in pass-through mode

iommu/amd: Do not set amd_iommu_pgtable in pass-through mode

Since AMD IOMMU page table is not used in passthrough mode, switching to
v1 page table is not required.

Therefore, remove redundant amd_iommu_pgtable update and misleading
warning message.

Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Link: https://lore.kernel.org/r/20230921092147.5930-7-vasant.hegde@amd.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>