Strange implementation of waitForInterrupt

The sequence
` __WFE();
__SEV(); // Clear Event Register.
__WFE();`
looks strange to me. SEV is supposed to set event register, not clear it, in which case the second WFE will always get through without stopping. So the first WFE is the one doing actual job, and should be sufficient by itself, IMHO

Locate waitForInterrupt in the repository and read its surrounding implementation, then verify the __WFE and __SEV behavior against the nRF52 or CMSIS documentation. Done means confirming whether the sequence is correct and recording the maintainer-approved implementation or rationale.

Written by the indexing model from the issue text.