sizeof(adapter) is larger than the big_entry->adapter and so the code
would copy too much. Instead only copy the strlen of the parsed
adapter, which we checked above to be smaller than the available size.
This doesn't copy the 0 byte because the memory is assumed to be 0
filled already by the calloc.
If the address is exactly the HCI_DEV_NAME_LEN, it will result in a non-0
terminated string, which may or may not be a problem...