SPI DMA TX link configuration
| OUTLINK_ADDR | The address of the first outlink descriptor. |
| OUTLINK_STOP | Set the bit to stop to use outlink descriptor. |
| OUTLINK_START | Set the bit to start to use outlink descriptor. |
| OUTLINK_RESTART | Set the bit to mount on new outlink descriptors. |
| DMA_TX_ENA | spi dma write data status bit. |