[SQUASH ME] netdev: adapt tests
[SQUASH ME] tests: check if pid in receive callback is correct
[SQUASH ME] netdev: move from set_event_handler() method to member variable
[SQUASH ME] netdev: remove some now unnecessary changes
cc2420: Port for netdev.802154
[SQUASH ME] cc2420: address comments
[SQUASH ME] cc2420: adapt for netdev event handler
[SQUASH ME] cc2420: adapt to changes in #2163