Fix compiling lwiperf_example.c with TCP disabled

examples/lwiperf/lwiperf_example.c

@@ -30,6 +30,7 @@
 #include "lwip/apps/lwiperf.h"
 #include "lwiperf_example.h"
 
+#if LWIP_TCP
 static void
 lwiperf_report(void *arg, enum lwiperf_report_type report_type,
   const ip_addr_t* local_addr, u16_t local_port, const ip_addr_t* remote_addr, u16_t remote_port,
@@ -42,9 +43,12 @@ lwiperf_report(void *arg, enum lwiperf_report_type report_type,
   printf("IPERF report: type=%d, remote: %s:%d, total bytes: %"U32_F", duration in ms: %"U32_F", kbits/s: %"U32_F"\n",
     (int)report_type, ipaddr_ntoa(remote_addr), (int)remote_port, bytes_transferred, ms_duration, bandwidth_kbitpsec);
 }
+#endif /* LWIP_TCP */
 
 void
 lwiperf_example_init(void)
 {
+#if LWIP_TCP
   lwiperf_start_tcp_server_default(lwiperf_report, NULL);
+#endif
 }