configure RTC GPIO15
| PAD_DRIVER | if set to 0: normal output, if set to 1: open drain |
| INT_TYPE | if set to 0: GPIO interrupt disable, if set to 1: rising edge trigger, if set to 2: falling edge trigger, if set to 3: any edge trigger, if set to 4: low level trigger, if set to 5: high level trigger |
| WAKEUP_ENABLE | RTC GPIO wakeup enable bit |