[Intel-gfx] Make init and mode set more asynchronous

[Jesse Barnes]

I'm worried about the locking in this...  I've also commented out the
state checker, but that can be re-added as a check after any queued CRTC
changes as another queued item, so should be easy to fix.

This set drastically improves the init time of the i915 module (based on
initcall_debug timing), and should allow suspend and resume to speed up
significantly too, but I'm still working on that.  Open items on the
suspend/resume path include:
  - synchronizing CRTC state against DP up/down (right now I synchronize
    which could be put off)
  - speeding up our DP hot plug on resume, it currently takes forever
    mostly due to VDD toggling.  I think Paulo's stuff should allow us
    to make this faster, but we still have some big delays here
  - get rid of the CRTC sync in the mode_set prepare_pipes; the sync
    just needs to happen before the enable CRTCs are actually enabled...
    so maybe queuing things in order is sufficient

Anyway I'd appreciate some eyes and feedback on this.

Thanks,
Jesse