iommu: Put domain allocation in __iommu_group_alloc_blocking_domain()

There is no longer a reason to call __iommu_domain_alloc() to allocate
the blocking domain. All drivers that support a native blocking domain
provide it via the ops, for other drivers we should call
iommu_paging_domain_alloc().

__iommu_group_alloc_blocking_domain() is the only place that allocates
an BLOCKED domain, so move the ops->blocked_domain logic there.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20241028093810.5901-12-vasant.hegde@amd.com


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