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>
(cherry picked from commit 09adb0e021207b60a0c51a68939b4539d98d3ef3)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>