Using drm_exec in TTM

[Christian König]

Hi guys,

while this works in an initial test I just realized that we need to
merge the GEM and TTM reference count first for it to be 100% reliable.

Otherwise it can be that we try to evict BOs which are in the process of
being torn down. And this in turn will result in a whole bunch of
problems.

So going to work on that first, just sending out the patch set once more
so that it won't get lost.

Regards,
Christian.