Merge pull request #6277 from bergzand/mrf24j40

drivers/Makefile.dep

drivers/Makefile.include

drivers/include/mrf24j40.h

drivers/mrf24j40/Makefile

drivers/mrf24j40/include/mrf24j40_internal.h

drivers/mrf24j40/include/mrf24j40_netdev.h

drivers/mrf24j40/include/mrf24j40_params.h

drivers/mrf24j40/include/mrf24j40_registers.h

drivers/mrf24j40/mrf24j40.c

drivers/mrf24j40/mrf24j40_getset.c

drivers/mrf24j40/mrf24j40_internal.c

drivers/mrf24j40/mrf24j40_netdev.c

pkg/lwip/contrib/lwip.c

sys/auto_init/auto_init.c

sys/auto_init/netif/auto_init_mrf24j40.c