digital saradc configure register
| SARADC_START_FORCE | select software enable saradc sample |
| SARADC_START | software enable saradc sample |
| SARADC_SAR_CLK_GATED | SAR clock gated |
| SARADC_SAR_CLK_DIV | SAR clock divider |
| SARADC_SAR_PATT_LEN | 0 ~ 15 means length 1 ~ 16 |
| SARADC_SAR_PATT_P_CLEAR | clear the pointer of pattern table for DIG ADC1 CTRL |
| SARADC_XPD_SAR_FORCE | force option to xpd sar blocks |
| SARADC_WAIT_ARB_CYCLE | wait arbit signal stable after sar_done |