lwip: fix build with CONFIG_LWIP_DHCPS disabled

Also added example build configuration for this option.

components/esp_netif/include/esp_netif_sta_list.h

@@ -42,6 +42,8 @@ typedef struct {
 /**
  * @brief  Get IP information for stations connected to the Wi-Fi AP interface
  *
+ * @note   If `CONFIG_LWIP_DHCPS` is disabled then `ip` address field will not be populated in sta list
+ *
  * @warning This API works only for the default Wi-Fi AP interface, i.e. esp-netif with key="WIFI_AP_DEF"
  *
  * @param[in]   wifi_sta_list Wi-Fi station info list, returned from esp_wifi_ap_get_sta_list()