hw/virtio: vdpa: Fix leak of host-notifier memory-region

hw/virtio: vdpa: Fix leak of host-notifier memory-region

If call virtio_queue_set_host_notifier_mr fails, should free
host-notifier memory-region.

This problem can trigger a coredump with some vDPA drivers (mlx5,
but not with the vdpasim), if we unplug the virtio-net card from
the guest after a stop/start.

The same fix has been done for vhost-user:
  1f89d3b91e3e ("hw/virtio: Fix leak of host-notifier memory-region")

Fixes: d0416d487bd5 ("vhost-vdpa: map virtqueue notification area if possible")
Cc: jasowang@redhat.com
Resolves: https://bugzilla.redhat.com/2027208
Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Message-Id: <20220211170259.1388734-1-lvivier@redhat.com>
Cc: qemu-stable@nongnu.org
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>