iperf: handle NO_MEM error in OpenThread iperf

* simplify iperf send/recv loop

components/lwip/port/esp32/netif/openthreadif.c

@@ -1,16 +1,8 @@
-// Copyright 2021 Espressif Systems (Shanghai) CO LTD
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License
-
+/*
+ * SPDX-FileCopyrightText: 2021 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
 #include <string.h>
 
 #include "esp_netif.h"
@@ -55,10 +47,15 @@ static err_t openthread_output_ip6(struct netif *netif, struct pbuf *p, const st
         pbuf_free(q);
     }
     /* Check error */
-    if (unlikely(ret != ESP_OK)) {
-        return ERR_ABRT;
-    } else {
+    switch(ret) {
+    case ESP_ERR_NO_MEM:
+        return ERR_MEM;
+
+    case ESP_OK:
         return ERR_OK;
+
+    default:
+        return ERR_ABRT;
     }
 }