modem sleep: add wifi power save callback to idle task

components/esp32/include/esp_wifi_internal.h

@@ -105,6 +105,15 @@ esp_err_t esp_wifi_internal_reg_rxcb(wifi_interface_t ifx, wifi_rxcb_t fn);
   */
 esp_err_t esp_wifi_internal_set_sta_ip(void);
 
+/**
+  * @brief     The WiFi power save callback function
+  *
+  * @param     none
+  *
+  * @return    none
+  */
+void esp_wifi_ps_idle_cb(void);
+
 #ifdef __cplusplus
 }
 #endif