intel-iommu: fail DEVIOTLB_UNMAP without dt mode

intel-iommu: fail DEVIOTLB_UNMAP without dt mode

Without dt mode, device IOTLB notifier won't work since guest won't
send device IOTLB invalidation descriptor in this case. Let's fail
early instead of misbehaving silently.

Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Tested-by: Laurent Vivier <lvivier@redhat.com>
Tested-by: Viktor Prutyanov <viktor@daynix.com>
Buglink: https://bugzilla.redhat.com/2156876
Signed-off-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20230223065924.42503-3-jasowang@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>