Add description and example for the vhost-user based RNG implementation.
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Message-Id: <20211012205904.4106769-4-mathieu.poirier@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>