I can only second @Max_G’s comment. There is barely a reason to restart a Linux system… at least not as often that one would need an automation mechanism in openHAB for it.
As for the binding: I don’t know the specifics there and why you would need to restart the Pi for the binding to work but in case of uncertainty you can restart openHAB to go all the way. Restarting the base system will not add anything.
See also:
Could you please link us to the source where it says to restart the Pi?