sensors: remove sensors_init

The initialization code is redundant and incomplete (only the first sensor
is done). I verified that all drivers already set this on startup.
For the mags, they all set their maximum supported update rate.
For the baro, the call can silently fail, as for example the MS5611 which
does not support 150Hz update. But it also sets the maximum in
initialization.

Tested on Pixhawk & pixracer.

src/modules/sensors/sensors.cpp

@@ -91,7 +91,6 @@
 
 #include <DevMgr.hpp>
 
-#include "sensors_init.h"
 #include "parameters.h"
 #include "rc_update.h"
 #include "voted_sensors_update.h"
@@ -158,11 +157,10 @@ public:
 	void	print_status();
 
 private:
-	/* XXX should not be here - should be own driver */
 	DevHandle 	_h_adc;				/**< ADC driver handle */
 	hrt_abstime	_last_adc;			/**< last time we took input from the ADC */
 
-	bool 		_task_should_exit;		/**< if true, sensor task should exit */
+	volatile bool 	_task_should_exit;		/**< if true, sensor task should exit */
 	int 		_sensors_task;			/**< task handle for sensor task */
 
 	const bool	_hil_enabled;			/**< if true, HIL is active */
@@ -553,23 +551,14 @@ void
 Sensors::task_main()
 {
 
-	/* start individual sensors */
 	int ret = 0;
 
 	if (!_hil_enabled) {
-		/* This calls a sensors_init which can have different implementations on NuttX, POSIX, QURT. */
-		ret = sensors_init();
-
 #if !defined(__PX4_QURT) && !defined(__PX4_POSIX_RPI) && !defined(__PX4_POSIX_BEBOP)
-		// TODO: move adc_init into the sensors_init call.
-		ret = ret || adc_init();
+		adc_init();
 #endif
 	}
 
-	if (ret) {
-		PX4_ERR("sensor initialization failed");
-	}
-
 	struct sensor_combined_s raw = {};
 
 	struct sensor_preflight_s preflt = {};