iommufd: Convert to alloc_domain_paging()

Move the global static blocked domain to the ops and convert the unmanaged
domain to domain_alloc_paging.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Acked-by: Sven Peter <sven@svenpeter.dev>
Link: https://lore.kernel.org/r/4-v2-bff223cf6409+282-dart_paging_jgg@nvidia.com


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