crypto: virtio - adjust priority of algorithm

Some hardware accelerators (like intel aesni or the s390
cpacf functions) have lower priorities than virtio
crypto, and those drivers are faster than the same in
the host via virtio. So let's lower the priority of
virtio-crypto's algorithm, make it's higher than software
implementations but lower than the hardware ones.

Suggested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Gonglei <arei.gonglei@huawei.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>