vdpa/mlx5: add virtq sub-resources creation

vdpa/mlx5: add virtq sub-resources creation

pre-created virt-queue sub-resource in device probe stage
and then modify virtqueue in device config stage.
Steer table also need to support dummy virt-queue.
This accelerates the LM process and reduces its time by 40%.

Signed-off-by: Li Zhang <lizh@nvidia.com>
Signed-off-by: Yajun Wu <yajunw@nvidia.com>
Acked-by: Matan Azrad <matan@nvidia.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>