Rate limit improvements for TTM

[Christian König]

Hi guys,

as already discussed on the mailing list Tvrtko and Friedrich stumbled
over a bunch of problems with the memory management. Especially that
move rate limit didn't seemed to work for VRAM|GTT BOs and causing bunch
of additional and unecessary overhead during CS.

This (not well tested) patch set tries to address some of those issues.
Especially patch #3 seems to fix some issues on APUs for the recently
introduced resume functionality.

I still need to do some more testing why the rate limit doesn't have the
desired effect sometimes.

Regards,
Christian.