Program the Key

1. Check the FIFOLEVEL register to monitor the amount of generated random numbers or wait for the FULLINT IRQ.
2. When FIFOLEVEL has reached the expected value or when an IRQ has been received, read the random numbers from the FIFO.
3. Use 4 x 32-bit random values to program a random key in the KEY register.
4. Apply software reset to flush the FIFO. By toggling the SOFTRST bit in the CONTROL register.