[Coverity CID :186845] Parse warnings in /tests/net/ieee802154/l2/src/ieee802154_test.c

[mandarcthorat1]

Static code scan issues seen in File: /tests/net/ieee802154/l2/src/ieee802154_test.c
Category: Parse warnings
Function:
Component: Tests
CID: 186845
Please fix or provide comments to square it off in coverity in the link: https://scan9.coverity.com/reports.htm#v32951/p12996

[jukkar]

False positive

[mandarcthorat1]

Fixed with #8645