[Nouveau] EVO class header files

[Andy Ritger]

A while ago, Ben Skeggs asked for some better documentation on EVO.  
Sorry it took a while, but here are the EVO class header files for NV50 
through GM204:

    ftp://download.nvidia.com/open-gpu-doc/Display-Class-Methods/1/

These header files define the method interface to the various EVO
channels.  There aren't descriptions of each method, but hopefully some
context can be gleaned from the method names.

Let me know if there are questions.

Thanks,
- Andy