APM_Control: SteerController: add active method

libraries/APM_Control/AP_SteerController.cpp

@@ -249,3 +249,9 @@ void AP_SteerController::reset_I()
 	_pid_info.I = 0;
 }
 
+// Returns true if controller has been run recently
+bool AP_SteerController::active() const
+{
+    return (AP_HAL::millis() - _last_t) < 1000;
+}
+

libraries/APM_Control/AP_SteerController.h

@@ -50,6 +50,9 @@ public:
         _reverse = reverse;
     }
 
+    // Returns true if controller has been run recently
+    bool active() const;
+
 private:
     AP_Float _tau;
 	AP_Float _K_FF;