[Intel-gfx] second cut at UXA with tiling

[Eric Anholt]

Here's a second set of patches for getting UXA working with tiling.  I think
it's correct on the UXA end of things now.  I've seen one rendering bug that
was probably GEM, and one that was probably xcompmgr.  I'm interested in any
feedback on what this API should be called.  Also, we now have API for each of

(CPU, 0)
(CPU, CPU)
(GTT, 0)
(GTT, GTT)

for doing software fallbacks.  Should this be rolled up somehow?  Not sure.

Note that if you're not running the latest patches from the for-review branch
of the kernel, things may be a little ugly.