AP_OpticalFlow: add range to POS param description

libraries/AP_OpticalFlow/OpticalFlow.cpp

@@ -45,18 +45,21 @@ const AP_Param::GroupInfo OpticalFlow::var_info[] = {
     // @DisplayName:  X position offset
     // @Description: X position of the optical flow sensor focal point in body frame. Positive X is forward of the origin.
     // @Units: m
+    // @Range: -10 10
     // @User: Advanced
 
     // @Param: _POS_Y
     // @DisplayName: Y position offset
     // @Description: Y position of the optical flow sensor focal point in body frame. Positive Y is to the right of the origin.
     // @Units: m
+    // @Range: -10 10
     // @User: Advanced
 
     // @Param: _POS_Z
     // @DisplayName: Z position offset
     // @Description: Z position of the optical flow sensor focal point in body frame. Positive Z is down from the origin.
     // @Units: m
+    // @Range: -10 10
     // @User: Advanced
     AP_GROUPINFO("_POS", 4, OpticalFlow, _pos_offset, 0.0f),