components esp32/lwip: modify code according to review comments

1. Modify comments for esp_wifi_internal_tx
2. Fix delay time error in esp32_tx_flow_ctrl which is found in code review,
   modify _wait_delay init value from 0 to 1

components/esp32/include/esp_wifi_internal.h

@@ -60,7 +60,7 @@ bool esp_wifi_internal_tx_is_stop(void);
 void esp_wifi_internal_free_rx_buffer(void* buffer);
 
 /**
-  * @brief  free the rx buffer which allocated by wifi driver
+  * @brief  transmit the buffer via wifi driver
   *
   * @attention1 TODO should modify the return type from bool to int
   * 

components/lwip/api/sockets.c

@@ -400,7 +400,7 @@ static void lwip_socket_drop_registered_memberships(int s);
  */ 
 static inline void esp32_tx_flow_ctrl(void)
 {
-  uint8_t _wait_delay = 0;
+  uint8_t _wait_delay = 1;
 
   while ((system_get_free_heap_size() < HEAP_HIGHWAT) || esp_wifi_internal_tx_is_stop()){
      vTaskDelay(_wait_delay/portTICK_RATE_MS);