[Intel-gfx] [RFC] ValleyView support

[Jesse Barnes]

In this set, you can see why I was asking about register offsets and
splitting the display code.  Included are a few cleanups to help me keep
my sanity, but as I mentioned in my other mail I think we should go
further.

Many of these are ok to apply as-is, so let me know what order you'd
like them in and I can re-post and work on the remainder.

Thanks,
Jesse