crypto: move 'opaque' parameter to (nearly) the end of parameter list

Previous commit moved 'opaque' to be the 2nd parameter in the list:

  commit 37509233
  Author: Fam Zheng <famz@redhat.com>
  Date:   Fri Apr 21 20:27:02 2017 +0800

    crypto: Make errp the last parameter of functions

    Move opaque to 2nd instead of the 2nd to last, so that compilers help
    check with the conversion.

this puts it back to the 2nd to last position.

Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>