iommu/vt-d: Replace Intel specific PASID allocator with IOASID

Make use of generic IOASID code to manage PASID allocation,
free, and lookup. Replace Intel specific code.

Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>