CEC driver compmatible with imx6 libcec

Hi
Here are commits which update the CEC driver so that it can work properly faced to https://github.com/xbmc-imx6/libcec
Main updates compared to the original freescale driver are
  * The ones described in this old blog [post](http://stephan-rafin.net/blog/2013/09/30/i-mx6-cec/)
  * Proper cec event on link connection/disconnection
  * Fix CEC clock which was disabled on some events (link connection and FB mode change)
  * Fix issue with cec interrupts which could be muted on link connection/disconnection
Best regards
Stephan