Update ESPmDNS.h

Author: Jason2866

libraries/ESPmDNS/src/ESPmDNS.h

@@ -38,6 +38,8 @@ License (MIT license):
   THE SOFTWARE.
 
 */
+#if CONFIG_MDNS_MAX_INTERFACES
+
 #ifndef ESP32MDNS_H
 #define ESP32MDNS_H
 
@@ -126,3 +128,4 @@ class MDNSResponder {
 extern MDNSResponder MDNS;
 
 #endif  //ESP32MDNS_H
+#endif /* CONFIG_MDNS_MAX_INTERFACES */