crypto: virtio - remove duplicate check if queue is broken

virtqueue_enable_cb() will call virtqueue_poll() which will check if
queue is broken at beginning, so remove the virtqueue_is_broken() call

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>