Plane: Fix param docs for quadplane attitude control

Docs aren't currently being generated for plane for AC_AttitudeControl.cpp. I believe this will fix that.

ArduPlane/Parameters.cpp

@@ -971,7 +971,7 @@ const AP_Param::Info Plane::var_info[] = {
     GOBJECT(tuning,           "TUNE_", AP_Tuning_Plane),
     
     // @Group: Q_A_
-    // @Path: ../libraries/AC_AttitudeControl/AC_AttitudeControl_Multi.cpp
+    // @Path: ../libraries/AC_AttitudeControl/AC_AttitudeControl.cpp,../libraries/AC_AttitudeControl/AC_AttitudeControl_Multi.cpp
     { AP_PARAM_GROUP, "Q_A_", Parameters::k_param_q_attitude_control,
       (const void *)&plane.quadplane.attitude_control,
       {group_info : AC_AttitudeControl_Multi::var_info}, AP_PARAM_FLAG_POINTER },