RFC: Radeon multi ring support branch

["Christian König" <deathsimple@vodafone.de>]

Hello everybody,

to support multiple compute rings, async DMA engines and UVD we need to 
teach the radeon kernel module how to sync buffers between different 
rings and make some changes to the command submission ioctls.

Since we can't release any documentation about async DMA or UVD (yet), 
my current branch concentrates on getting the additional compute rings 
on cayman running. Unfortunately those rings have hardware bugs that 
can't be worked around, so they are actually not very useful in a 
production environment, but they should do quite well for this testing 
purpose.

The branch can be found here: 
http://cgit.freedesktop.org/~deathsimple/linux/log/

Since some of the patches are quite intrusive, constantly rebaseing them 
could get a bit painful. So I would like to see most of the stuff 
included into drm-next, even if we don't make use of the new 
functionality right now.

Comments welcome,
Christian.