anv: Rework fences to work more like BO semaphores

This commit changes fences to work a bit more like BO semaphores.
Instead of the fence being a batch, it's simply a BO that gets added
to the validation list for the last execbuf call in the QueueSubmit
operation.  It's a bit annoying finding the last submit in the execbuf
but this allows us to avoid the dummy execbuf.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
3 files changed