Just flash in stock recovery. You may need to change response from "allow" to "prompt" in super user settings.
https://www.dropbox.com/s/0s0tosfbq23nmxl/Superuser-3.1.3-arm-signed.zip?dl=0
https://www.dropbox.com/s/0s0tosfbq23nmxl/Superuser-3.1.3-arm-signed.zip?dl=0