crypto engine was introduced since 'commit 735d37b5424b ("crypto: engine
- Introduce the block request crypto engine framework")' which uses work
queue to realize the asynchronous processing for ablk_cipher and ahash.

For virtio-crypto device, I register an engine for each
data virtqueue so that we can use the capability of
multiple data queues in future.

Cc: Baolin Wang <baolin.wang@linaro.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Gonglei <arei.gonglei@huawei.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

This patch introduces virtio-crypto driver for Linux Kernel.

The virtio crypto device is a virtual cryptography device
as well as a kind of virtual hardware accelerator for
virtual machines. The encryption anddecryption requests
are placed in the data queue and are ultimately handled by
thebackend crypto accelerators. The second queue is the
control queue used to create or destroy sessions for
symmetric algorithms and will control some advanced features
in the future. The virtio crypto device provides the following
cryptoservices: CIPHER, MAC, HASH, and AEAD.

For more information about virtio-crypto device, please see:
  http://qemu-project.org/Features/VirtioCrypto

CC: Michael S. Tsirkin <mst@redhat.com>
CC: Cornelia Huck <cornelia.huck@de.ibm.com>
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Herbert Xu <herbert@gondor.apana.org.au>
CC: Halil Pasic <pasic@linux.vnet.ibm.com>
CC: David S. Miller <davem@davemloft.net>
CC: Zeng Xin <xin.zeng@intel.com>
Signed-off-by: Gonglei <arei.gonglei@huawei.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>