The ITE 8893 bridge has the same problems as the ITE 8892, which were
resulting in crippling an older PCI 1Gbps NIC down to 45Mbps throughput
with IOMMU and VT-d enabled.  With the patch, this old e1000 goes back up
to ~900Mbps.
Suggested-by: NAlex Williamson <alex.williamson@redhat.com>
Signed-off-by: NJarod Wilson <jarod@redhat.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NAlex Williamson <alex.williamson@redhat.com>