tests: fix netdev test
Merge pull request #1761 from authmillenon/netdev-fix

tests: fix netdev test
cpu/stm32f0: removed leftovers from slave mode
Merge pull request #1713 from haukepetersen/fix_stm32f0_spi

cpu/stm32f0: removed leftovers from slave mode
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
[SQUASH ME] whitelist arduino-due for nrf24l01p lowlevel test