vhost_scsi: convert to vhost_vq_work_queue

Convert from vhost_work_queue to vhost_vq_work_queue so we can
remove vhost_work_queue.

Signed-off-by: Mike Christie <michael.christie@oracle.com>
Message-Id: <20230626232307.97930-11-michael.christie@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>