atmega_common: add ENOTSUP and ECANCELED to errno.h
drivers: Provide basic interface for all network devices
tests: Add functionality test for netdev_base
Merge pull request #1492 from authmillenon/net-dev-base

drivers: Introduce a general interface for network device drivers
Initial import of nrf24l01p lowlevel functions
[SQUASM ME] removed tests/test_spi
[SQUASH ME] changed delay after function call
[SQUASH ME] removed netdev includes from drivers/makefile
[SQUASH ME] update some small things to changes caused by netdev in another PR
[SQUASH ME] added a small REAMDE to describe the usage of the test