Function esp_wifi_sta_get_negotiated_phymode 

pub unsafe extern "C" fn esp_wifi_sta_get_negotiated_phymode(
    phymode: *mut wifi_phy_mode_t,
) -> esp_err_t

@brief Get the negotiated phymode after connection.

@param[out] phymode store the negotiated phymode.

@return

• ESP_OK: succeed
• ESP_ERR_WIFI_NOT_STARTED: WiFi is not started by esp_wifi_start
• ESP_ERR_WIFI_NOT_CONNECT: No connection between STA and AP