oldnet: remove radio_packet_length_t define

boards/avsextrem/include/board.h

boards/chronos/include/board.h

boards/fox/include/board.h

boards/frdm-k64f/include/board.h

boards/iot-lab_M3/include/board.h

boards/mbed_lpc1768/include/board.h

boards/msb-430/include/board.h

boards/msb-430h/include/board.h

boards/msbiot/include/board.h

boards/mulle/include/board.h

boards/native/include/board.h

boards/nucleo-f091/include/board.h

boards/nucleo-f303/include/board.h

boards/nucleo-f334/include/board.h

boards/nucleo-l1/include/board.h

boards/pba-d-01-kw2x/include/board.h

boards/pttu/include/board.h

boards/redbee-econotag/include/board.h

boards/samr21-xpro/include/board.h

boards/spark-core/include/board.h