add const keyword for sensor ops

components/drivers/sensors/sensor.h

@@ -140,7 +140,7 @@ struct rt_sensor_device
     void                        *data_buf;  /* The buf of the data received */
     rt_size_t                    data_len;  /* The size of the data received */
 
-    struct rt_sensor_ops        *ops;       /* The sensor ops */
+    const struct rt_sensor_ops  *ops;       /* The sensor ops */
 
     struct rt_sensor_module     *module;    /* The sensor module */
 };