[Intel-gfx] [RFC v6] refactor intel display a bit more

[Dave Airlie]

Okay the first 8 patches of this should probably get landed, they have
all the tags in place.

The subsequent patches have seen some rework:
Added a patch to move the buf_trans to a separate file as suggested
by Ville. I reworked some of the interfaces while doing so, but only
minorly.

The skl planes code no long moves any scaler code.

Some more ppl moving code, and a piece of forgotten i9xx plane moved.

Dave.