[Open-graphics] HQ stub in place

[Petter Urkedal]

On 2008-07-30, Timothy Normand Miller wrote:
> > I don't think we can.  val_or_addr comes directly from res_o of the ALU,
> > which by the way already is MUXed after registration.
> 
> Ok, then we'll just have to see how it goes.  We'll wire it up and try it.

I submitted a revision which assumed the port read data is passed
combinatorially back to HQ.  You can find a matching but rather sketchy
bridge wrapper on
http://www.eideticdew.org/~urkedal/ogp/xp10_bridge_wrapper.v.
It has a number of TODOs, CHECKMEs, and FIXMEs.  In particular, I
didn't find a signal from PCI which indicates the target of the command,
and I wasn't sure how to indicate memory vs engine addresses to the
bridge.