keyspan_put_tail
keyspan_put_tail(&kp->kp_tx_mp, mp); /* add to the chain */
keyspan_put_tail(&kp->kp_rx_mp, mp);
keyspan_put_tail(&kp->kp_rx_mp, mp);
keyspan_put_tail(&kp->kp_rx_mp, data);
keyspan_put_tail(&kp_true->kp_rx_mp, mp_data);
void keyspan_put_tail(mblk_t **, mblk_t *);