Add #include "FreeRTOS_ARP.h" to loopbackNetworkInterface.c (#1290)

To resolve the issue #1289

Author: Nikolay-Po

source/portable/NetworkInterface/loopback/loopbackNetworkInterface.c

@@ -35,6 +35,7 @@
 #include "semphr.h"
 
 /* FreeRTOS+TCP includes. */
+#include "FreeRTOS_ARP.h"
 #include "FreeRTOS_IP.h"
 #include "FreeRTOS_Sockets.h"
 #include "FreeRTOS_IP_Private.h"