Merge pull request #6797 from aabadie/driver_sx127x

cpu/cc2538/radio/cc2538_rf_getset.c

drivers/Makefile.dep

drivers/Makefile.include

drivers/include/net/netdev.h

drivers/include/sx127x.h

drivers/sx127x/Makefile

drivers/sx127x/include/sx127x_internal.h

drivers/sx127x/include/sx127x_netdev.h

drivers/sx127x/include/sx127x_params.h

drivers/sx127x/include/sx127x_registers.h

drivers/sx127x/sx127x.c

drivers/sx127x/sx127x_getset.c

drivers/sx127x/sx127x_internal.c

drivers/sx127x/sx127x_netdev.c

makefiles/pseudomodules.inc.mk

sys/include/net/netopt.h

sys/net/crosslayer/netopt/netopt.c

tests/driver_sx127x/Makefile

tests/driver_sx127x/README.md

tests/driver_sx127x/main.c