AP_Landing: emit DEPLOY gcs text only if not already deployed

libraries/AP_LandingGear/AP_LandingGear.cpp

@@ -122,14 +122,15 @@ void AP_LandingGear::deploy()
     // set servo PWM to deployed position
     SRV_Channels::set_output_limit(SRV_Channel::k_landing_gear_control, SRV_Channel::SRV_CHANNEL_LIMIT_MAX);
 
-    // set deployed flag
-    _deployed = true;
-    _have_changed = true;
-
     // send message only if output has been configured
-    if (SRV_Channels::function_assigned(SRV_Channel::k_landing_gear_control)) {
+    if (!_deployed &&
+        SRV_Channels::function_assigned(SRV_Channel::k_landing_gear_control)) {
         gcs().send_text(MAV_SEVERITY_INFO, "LandingGear: DEPLOY");
     }
+
+    // set deployed flag
+    _deployed = true;
+    _have_changed = true;
 }
 
 /// retract - retract landing gear