bmp388: quiet if startup fails (no sensor on bus)

src/drivers/barometer/bmp388/bmp388.cpp

@@ -66,7 +66,7 @@ int
 BMP388::init()
 {
 	if (!soft_reset()) {
-		PX4_WARN("failed to reset baro during init");
+		PX4_DEBUG("failed to reset baro during init");
 		return -EIO;
 	}