Introduce the virtio crypto realization, I'll
finish the core code in the following patches. The
thoughts came from virtio net realization.

For more information see:
http://qemu-project.org/Features/VirtioCryptoSigned-off-by: NGonglei <arei.gonglei@huawei.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>