Update ESPmDNS.cpp

Author: Jason2866

libraries/ESPmDNS/src/ESPmDNS.cpp

@@ -38,6 +38,8 @@ License (MIT license):
 #define LWIP_OPEN_SRC
 #endif
 
+#if CONFIG_MDNS_MAX_INTERFACES
+
 #include "ESPmDNS.h"
 #include <functional>
 #include "esp_mac.h"
@@ -391,3 +393,5 @@ String MDNSResponder::txtKey(int idx, int txtIdx) {
 }
 
 MDNSResponder MDNS;
+
+#endif /* CONFIG_MDNS_MAX_INTERFACES */