修改udhcpc参数，停用wifi时，释放申请到的ip

pro/src/wifi.c

@@ -113,7 +113,7 @@ static int sta_start(ap_info_t *info, int on)
         sprintf(tmp, "wpa_supplicant -B -i %s -c %s", WLAN_IFNAME, STA_CONF);
         r = system(tmp);
 
-        sprintf(tmp, "udhcpc -b -i %s", WLAN_IFNAME);
+        sprintf(tmp, "udhcpc -R -b -i %s", WLAN_IFNAME);
         r = system(tmp);
     }
     else {