[Mesa-dev] MR: Anv: document & improve pipeline flushes/invalidates

[Lionel Landwerlin]

https://gitlab.freedesktop.org/mesa/mesa/merge_requests/132

2 change in this MR :

     * add some documentation to clarify how we choose pipeline flushes 
invalidations
     * narrow the CS stall & RT flushes for the query copies to track 
only operations that write a destination buffer

For the second change we have crucible test bug.108909 to verify that 
this is still correct.

-
Lionel