How to UNROOT EVA-L19 for update via OTA?

How to UNROOT EVA-L19 for update via OTA? Just uninstall supersu?
Do I have before OTA update again locked bootloader?
Thanks for advice.

Stock ROM dload file - P9 EVA-L19 B162

Hi
This is dload file for L19 version , latest update B162
1- download the file
2- unzip it and copy dload file to sdcard
3- power off the device
4- press and hold all the buttons [vol up + down + power buttons]
5- still hold until the device start flashing
6- DONE!

Download Link from HERE