TX CH2 out_link dscr ctrl register
| OUTLINK_STOP_CH2 | Set this bit to stop dealing with the outlink descriptors. |
| OUTLINK_START_CH2 | Set this bit to start dealing with the outlink descriptors. |
| OUTLINK_RESTART_CH2 | Set this bit to restart a new outlink from the last address. |
| OUTLINK_PARK_CH2 | 1: the outlink descriptor’s FSM is in idle state. 0: the outlink descriptor’s FSM is working. |