src: mqtt: Use simpler struct instanciation syntax

src/mqtt.rs

@@ -54,13 +54,12 @@ impl MQTT {
         mqttoptions.set_keep_alive(Duration::from_secs(5));
 
         let (client, eventloop) = AsyncClient::new(mqttoptions, 1);
-        let mqtt = MQTT {
-            config: config,
-            client: client,
-            eventloop: eventloop,
-        };
 
-        mqtt
+        MQTT {
+            config,
+            client,
+            eventloop,
+        }
     }
 
     pub async fn subscribe<F: Fn(StatusMessage)>(&mut self, callback: F) -> Result<()> {