The buffer allocated with length "ATH6KL_FWLOG_PAYLOAD_SIZE"
is not initialized, this may lead to information leak during
memcpy when len < ATH6KL_FWLOG_PAYLOAD_SIZE.
To resolve this issue, memset the buffer for length
(ATH6KL_FWLOG_PAYLOAD_SIZE - len) to 0
Change-Id: If4a49347d674ad2af0438b408a4a4b9308c61026
CRs-Fixed: 2255083