I have done the following:
1) Unlock bootloader (first make a backup).
2) Download SuperSu.zip and copy in memory. (Last versionhttp://download.chainfire.eu/supersu)
3) Download fastboot.rar and extract. (fastboot.rar inlcudes boot.img (doomkernel) for flash). 
4) Place fastboot folder in C:
5) Open cmd (from start) and go to C:/fastboot
6) Plug phone in fastboot mode (shoutdown and press Vol + and plug usb).
7) In cmd write “fastboot flash boot boot.img” at the end “fastboot reboot”.
8) Enter in recovery pressing vol + or vol – when phone booting and led is coloured.
9) Flash supersu.zip. Unplug usb.
10) After go in advanced and shoutdown phone (NOT RESTART).
11) Flash ONLY stock kernel of your firmware with flashtool. Reboot.
12) Relock bootloader.

Fastboot.rar
https://mega.co.nz/#!U5pkQQ6T!5YAVu3…fg_R-JEBoJ25cM