git: drm/ttm: Sync ttm_execbuf_util.c with Linux

[Michael Neumann]

On Sun, Nov 11, 2018 at 12:40:12AM -0800, Francois Tigeot wrote:
> 
> commit fb15202ca65065a9db8fb9fd523efd6e11c370c7
> Author: François Tigeot <ftigeot at wolfpond.org>
> Date:   Sun Nov 11 09:18:03 2018 +0100
> 
>     drm/ttm: Sync ttm_execbuf_util.c with Linux

One of the recent commits to drm/ttm introduced a regression.

I tried HEAD as of today and it will freeze the display and any input
device after some time working in graphics mode (30 minutes or so). The
computer is still working, I can ssh into it... but I can't change to
the terminal from X11 via ALT-F1 or move the mouse.

This commit is still working: d709dbd65baeadb614dc2896b69e5c0dedb873d9.
>From there on, I can bisect to find the relevant commit if that helps.
If you need a core dump, let me know.

Regards,

  Michael