Function esp_wifi_get_band_mode 

pub unsafe extern "C" fn esp_wifi_get_band_mode(
    band_mode: *mut u32,
) -> i32

@brief get WiFi band mode.

@param[in] band_mode store the band mode of WiFi

@return

• ESP_OK: succeed
• ESP_ERR_WIFI_NOT_INIT: WiFi is not initialized by esp_wifi_init
• ESP_ERR_INVALID_ARG: invalid argument