CF/BF - Delete unused BST code.

CF/BF - Delete unused BST code.

"[20/03/2017, 13:46:12] Remo Masina: This is a list of al the frames we
currently use:

BST_MAG_CALIBRATION,
BST_ACC_CALIBRATION,
BST_SET_PID,
BST_SET_RC_TUNING,
BST_SET_LOOP_TIME,
BST_SELECT_SETTING,
BST_SET_RX_MAP,
BST_SET_MISC,
BST_SET_DEADBAND,
BST_SET_FC_FILTERS,
BST_SET_FEATURE,
BST_SET_RX_CONFIG,
BST_SET_MODE_RANGE,
BST_SET_LED_COLORS,
BST_EEPROM_WRITE,
BST_REBOOT,
BST_DISARM,
BST_ENABLE_ARM,

BST_PID,
BST_STATUS,
BST_RC_TUNING,
BST_LOOP_TIME,
BST_RX_MAP,
BST_MISC,
BST_DEADBAND,
BST_FC_FILTERS,
BST_FEATURE,
BST_RX_CONFIG"

See here:
https://github.com/cleanflight/cleanflight/pull/2664#issuecomment-287764706