spapr_iommu: Fix vhost integration regression

spapr_iommu: Fix vhost integration regression

Previous work on dev-iotlb message broke spapr_iommu/vhost integration
as it did for SMMU and virtio-iommu. The spapr_iommu currently
only sends IOMMU_NOTIFIER_UNMAP notifications. Since commit
958ec334bca3 ("vhost: Unbreak SMMU and virtio-iommu on dev-iotlb support"),
VHOST first tries to register IOMMU_NOTIFIER_DEVIOTLB_UNMAP notifier
and if it fails, falls back to legacy IOMMU_NOTIFIER_UNMAP. So
spapr_iommu must fail on the IOMMU_NOTIFIER_DEVIOTLB_UNMAP
registration.

Reported-by: Peter Xu <peterx@redhat.com>
Fixes: b68ba1ca5767 ("memory: Add IOMMU_NOTIFIER_DEVIOTLB_UNMAP IOMMUTLBNotificationType")
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Message-Id: <20210209213233.40985-3-eric.auger@redhat.com>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>