remove BOARD_NAME from board_config.h and set automatically

boards/aerotenna/ocpoc/src/board_config.h

boards/airmind/mindpx-v2/src/board_config.h

boards/atlflight/eagle/src/board_config.h

boards/atlflight/excelsior/src/board_config.h

boards/atmel/same70xplained/src/board_config.h

boards/auav/esc35-v1/src/board_config.h

boards/auav/x21/src/board_config.h

boards/av/x-v1/src/board_config.h

boards/beaglebone/blue/src/board_config.h

boards/bitcraze/crazyflie/src/board_config.h

boards/emlid/navio2/src/board_config.h

boards/gumstix/aerocore2/src/board_config.h

boards/intel/aerofc-v1/src/board_config.h

boards/nxp/hlite-v3/src/board_config.h

boards/omnibus/f4sd/src/board_config.h

boards/parrot/bebop/src/board_config.h

boards/px4/cannode-v1/src/board_config.h

boards/px4/esc-v1/src/board_config.h

boards/px4/fmu-v2/src/board_config.h

boards/px4/fmu-v3/src/board_config.h