Hotfix: Completely silencing HMC5883 probing to not confuse users

src/drivers/hmc5883/hmc5883.cpp

@@ -329,7 +329,7 @@ HMC5883::HMC5883(int bus) :
 	_calibrated(false)
 {
 	// enable debug() calls
-	_debug_enabled = true;
+	_debug_enabled = false;
 
 	// default scaling
 	_scale.x_offset = 0;
@@ -1224,12 +1224,10 @@ start()
 		errx(1, "already started");
 
 	/* create the driver, attempt expansion bus first */
-	warnx("probing for external sensor..");
 	g_dev = new HMC5883(PX4_I2C_BUS_EXPANSION);
 	if (g_dev != nullptr && OK != g_dev->init()) {
 		delete g_dev;
 		g_dev = nullptr;
-		warnx("no external sensor, using internal..");
 	}