[Intel-gfx] Shuffled full-ppgtt vma binding performance fix

[Daniel Vetter]

So I've finally gotten around to shuffle these patches a bit more and hopefully
in the process cleared up any lingering misunderstandings I've had about Chris'
originally patch.

I'll pull this in later today (presuming nothing bad shows up) and then cut a
new -testing before heading off for 2 weeks of vacation.

Cheers, Daniel