anv: fix index buffer emission

In the following case :

  vkCmdBindPipeline(compute_pipeline);
  vkCmdDispatch(...);
  vkCmdBindPipeline(graphics_pipeline);
  vkCmdBindIndexBuffer(buffer)
  vkCmdDraw(...);

We're emitting the 3DSTATE_INDEX_BUFFER instruction while the HW is still in GPGPU mode, because we're dealing the pipeline selection in vkCmdDraw().

Found while debugging Age Of Empire 4, HW is hung on 3DSTATE_INDEX_BUFFER instruction.

Signed-off-by: Lionel Landwerlin lionel.g.landwerlin@intel.com Cc: mesa-stable