Address of local variable buffer is assigned to a non-local variable

https://github.com/ARMmbed/DAPLink/blob/06fa0a9ca76a0f4b2732b030ebbcba9e6e20a708/source/board/microbitv2/nrf52820/pwr_mon_adc.c#L76

A stack address is assigned to a non-local variable. Storing the address of a local variable in non-local memory can cause a dangling pointer bug if the address is used after the function returns.

Start at source/board/microbitv2/nrf52820/pwr_mon_adc.c:76 and inspect the local buffer, the non-local variable receiving its address, and callers that use it. Determine how to prevent the address from outliving the local variable, then verify the affected power-monitoring behavior on the relevant firmware target.

Written by the indexing model from the issue text.