core/linux-wandboard enable cec

This patches the kernel with wolfgars modified imx-cec driver (https://github.com/wolfgar/linux-linaro-stable-mx6/commit/74fc2e85c080b0ddc2a4b2565eda97c55300303d and https://github.com/wolfgar/linux-linaro-stable-mx6/commit/76796e32b20dd8f34aadad8fd91672017d143812, see xbmc-imx6/xbmc#54).

It also enables cec in the dts file, this should work if the board is either rev c or has been [modified](https://www.project-insanity.org/blog/2014/01/24/wandboard-with-hdmi-cec-and-xbmc/).

I have verified that this works, it even survives turning the tv off and on again.

Cheers