[Intel-gfx] [RFC] Deep color support

[Jesse Barnes]

This collection of patches sits on top of my two DRM EDID patches to fetch
display color format support.  They fix a few bugs in our depth handling
code, and allow for deep color configurations to be enabled in the core
display code (still working on good tests for this).

Looking for comments on how things are split out and lots of review for
implications on various chipsets.

Thanks,
Jesse