[SQUASH ME] netdev: add pointer for more driver dependent information
[SQUASH ME] cc2420: adapt for *more*
[SQUASH ME] nativenet: adapt for *more*
[SQUASH ME] net_dev/default.h: simplify thanks to *more*
[SQUASH ME] netdev_dummy: adapt to *more*
[SQUASH ME] unittests: adapt to previous changes in netdev_dummy
[SQUASH ME] tests: adapt functionality tests for previous changes