virtio-crypto: set capacity of algorithms supported

Expose the capacity of algorithms supported by
virtio crypto device to the frontend driver using
pci configuration space.

Signed-off-by: Gonglei <arei.gonglei@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
