I just wanted to post this here in case somebody else has with problem.
Problem:
After the Kodi update from 14 to 15 (Isengard) CEC stopped working.
Solution:
Install "libcec-rpi" that will replace an old version of "libcec".
"kodi-rbp" already depends on "libcec-rpi" so usually it should have been installed automatically. I don't know why I had to update it manually.