SPI DMA TX status
| DMA_OUTDSCR_ADDR | SPI dma out descriptor address. |
| DMA_OUTDSCR_STATE | SPI dma out descriptor state. |
| DMA_OUT_STATE | SPI dma out data state. |
| DMA_OUTFIFO_CNT | The remains of SPI dma outfifo data. |
| DMA_OUTFIFO_FULL | SPI dma outfifo is full. |
| DMA_OUTFIFO_EMPTY | SPI dma outfifo is empty. |