esp32/docs: fully support esp_wifi_80211_tx

Closes https://github.com/espressif/esp-idf/issues/1256
Closes https://github.com/espressif/esp-idf/issues/1332

components/esp32/include/esp_wifi.h

@@ -929,6 +929,32 @@ esp_err_t esp_wifi_set_event_mask(uint32_t mask);
   */
 esp_err_t esp_wifi_get_event_mask(uint32_t *mask);
 
+/**
+  * @brief     Send raw ieee80211 data
+  *
+  * @attention Currently only support for sending beacon/probe request/probe response/action and non-QoS
+  *            data frame
+  * 
+  * @param     ifx interface if the Wi-Fi mode is Station, the ifx should be WIFI_IF_STA. If the Wi-Fi
+  *            mode is SoftAP, the ifx should be WIFI_IF_AP. If the Wi-Fi mode is Station+SoftAP, the 
+  *            ifx should be WIFI_IF_STA or WIFI_IF_AP. If the ifx is wrong, the API returns ESP_ERR_WIFI_IF.
+  * @param     buffer raw ieee80211 buffer
+  * @param     len the length of raw buffer, the len must be <= 1500 Bytes and >= 24 Bytes
+  * @param     en_sys_seq indicate whether use the internal sequence number. If en_sys_seq is false, the 
+  *            sequence in raw buffer is unchanged, otherwise it will be overwritten by WiFi driver with 
+  *            the system sequence number.
+  *            Generally, if esp_wifi_80211_tx is called before the Wi-Fi connection has been set up, both
+  *            en_sys_seq==true and en_sys_seq==false are fine. However, if the API is called after the Wi-Fi
+  *            connection has been set up, en_sys_seq must be true, otherwise ESP_ERR_WIFI_ARG is returned.
+  *
+  * @return
+  *    - ESP_OK: success
+  *    - ESP_ERR_WIFI_IF: Invalid interface
+  *    - ESP_ERR_INVALID_ARG: Invalid parameter
+  *    - ESP_ERR_WIFI_NO_MEM: out of memory
+  */
+
+esp_err_t esp_wifi_80211_tx(wifi_interface_t ifx, const void *buffer, int len, bool en_sys_seq);
 
 #ifdef __cplusplus
 }