crypto: add virtio-crypto driver

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: Gon...