iOS on the iPhone or on any other iOS device does not provide you home screen icons to perform reboot or respring operations. Fortunately, there is a jailbreak tweak for that. To get those icons on the homescreen, all you have to do is download a tweak called PowerIcons.
Simply open Cydia and search for powericons. After installing it, you will find four icons on your homscreen – shutdown, respring, reboot and safe mode.