Respin: drm vblank regression fixes for Linux 4.4+ (v2)

[Mario Kleiner]

Here the respin of my series of vblank bug fixes for stable
Linux 4.4/4.5 with all review comments by Daniel and Ville
taken into account and reviewd-by's and tested-by's added.

I've removed the stable patch "drm: Prevent vblank counter jumps
with timestamp based update method." for the moment. I'll send a
respin of that patch later for drm-next / Linux 4.6, taking
Daniels and Villes comments into account.

Instead a stable patch 6/6 for nouveau now solves the problem of large
vblank counter jumps for that driver on suspend/resume. As nouveau is
currently the only user of the timestamping based vblank counter path,
this should fix that regression properly for Linux 4.4/4.5. Tested with
a couple of suspend/resume cycles composited/non-composited, with/without
vblank clients on a laptop with nv-50.

thanks,
-mario