lsm9ds1: cleanup + consistency with other drivers

src/drivers/imu/st/lsm9ds1/LSM9DS1.cpp

@@ -73,20 +73,23 @@ int LSM9DS1::probe()
 	return PX4_ERROR;
 }
 
-bool LSM9DS1::Init()
+int LSM9DS1::init()
 {
-	if (SPI::init() != PX4_OK) {
-		return false;
+	int ret = SPI::init();
+
+	if (ret != OK) {
+		DEVICE_DEBUG("SPI init failed (%i)", ret);
+		return ret;
 	}
 
 	if (!Reset()) {
 		PX4_ERR("reset failed");
-		return false;
+		return PX4_ERROR;
 	}
 
 	Start();
 
-	return true;
+	return PX4_OK;
 }
 
 bool LSM9DS1::Reset()
@@ -172,18 +175,11 @@ void LSM9DS1::RegisterClearBits(Register reg, uint8_t clearbits)
 
 void LSM9DS1::Start()
 {
-	Stop();
-
 	ResetFIFO();
 
 	ScheduleOnInterval(_fifo_interval / 2, _fifo_interval);
 }
 
-void LSM9DS1::Stop()
-{
-	ScheduleClear();
-}
-
 void LSM9DS1::RunImpl()
 {
 	perf_count(_interval_perf);

src/drivers/imu/st/lsm9ds1/LSM9DS1.hpp

@@ -66,9 +66,9 @@ public:
 	static void print_usage();
 	void     print_status();
 
-	bool     Init();
+	int     init() override;
+
 	void     Start();
-	void     Stop();
 	bool     Reset();
 
 	void     RunImpl();

src/drivers/imu/st/lsm9ds1/lsm9ds1_main.cpp

@@ -47,7 +47,7 @@ I2CSPIDriverBase *LSM9DS1::instantiate(const BusCLIArguments &cli, const BusInst
 		return nullptr;
 	}
 
-	if (!instance->Init()) {
+	if (OK != instance->init()) {
 		delete instance;
 		return nullptr;
 	}