iommu/vt-d: Use ops->blocked_domain

Trivially migrate to the ops->blocked_domain for the existing global
static.

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
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/3-v2-bff223cf6409+282-dart_paging_jgg@nvidia.com


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