removed stm discovery board.

Signed-off-by: Claudio Micheli <claudio@auterion.com>

boards/stm/32f4discovery/default.cmake

-
-px4_add_board(
-	PLATFORM nuttx
-	VENDOR stm
-	MODEL 32f4discovery
-	TOOLCHAIN arm-none-eabi
-	ARCHITECTURE cortex-m4
-	ROMFSROOT px4fmu_common
-	#TESTING
-
-	DRIVERS
-		#barometer # all available barometer drivers
-		#batt_smbus
-		#camera_trigger
-		#differential_pressure # all available differential pressure drivers
-		#distance_sensor # all available distance sensor drivers
-		#gps
-		#heater
-		#imu # all available imu drivers
-		#irlock
-		#lights/blinkm
-		#lights/oreoled
-		#lights/rgbled
-		#magnetometer # all available magnetometer drivers
-		#mkblctrl
-		#pca9685
-		#pwm_input
-		#pwm_out_sim
-		#px4flow
-		#px4fmu
-		#rc_input
-		stm32
-		#stm32/adc
-		#stm32/tone_alarm
-		#tap_esc
-		#telemetry # all available telemetry drivers
-		#test_ppm
-		#uavcan
-
-	MODULES
-		attitude_estimator_q
-		camera_feedback
-		commander
-		dataman
-		ekf2
-		events
-		fw_att_control
-		fw_pos_control_l1
-		gnd_att_control
-		gnd_pos_control
-		land_detector
-		landing_target_estimator
-		load_mon
-		local_position_estimator
-		logger
-		mavlink
-		#mc_att_control
-		#mc_pos_control
-		#navigator
-		position_estimator_inav
-		#sensors
-		#vmount
-		#vtol_att_control
-		wind_estimator
-
-	SYSTEMCMDS
-		bl_update
-		config
-		dumpfile
-		esc_calib
-		hardfault_log
-		led_control
-		mixer
-		motor_ramp
-		motor_test
-		mtd
-		nshterm
-		param
-		perf
-		pwm
-		reboot
-		reflect
-		sd_bench
-		shutdown
-		#tests # tests and test runner
-		top
-		topic_listener
-		tune_control
-		usb_connected
-		ver
-
-	EXAMPLES
-		bottle_drop # OBC challenge
-		fixedwing_control # Tutorial code from https://px4.io/dev/example_fixedwing_control
-		hello
-		#hwtest # Hardware test
-		#matlab_csv_serial
-		#publisher
-		px4_mavlink_debug # Tutorial code from https://px4.io/dev/debug_values
-		px4_simple_app # Tutorial code from https://px4.io/dev/px4_simple_app
-		rover_steering_control # Rover example app
-		segway
-		#subscriber
-		uuv_example_app
-
-	)