[MQTT] Fixed exclusion macros

src/protocols/MQTT/MQTT.h

@@ -1,7 +1,10 @@
-#if !defined(_RADIOLIB_MQTT_H) && !defined(RADIOLIB_EXCLUDE_MQTT)
+#if !defined(_RADIOLIB_MQTT_H)
 #define _RADIOLIB_MQTT_H
 
 #include "../../TypeDef.h"
+
+#if !defined(RADIOLIB_EXCLUDE_MQTT)
+
 #include "../TransportLayer/TransportLayer.h"
 
 // MQTT packet types
@@ -140,3 +143,5 @@ class MQTTClient {
 };
 
 #endif
+
+#endif