draw: flush when setting stream-out targets
We need to re-prepare the middle-end state to pick up changes to this state to react correctly to pausing/resuming stream-out. So let's add a flush here. Signed-off-by:Erik Faye-Lund <erik.faye-lund@collabora.com> Fixes: ec8cbd79 "draw/softpipe: EXT_transform_feedback support (v2)" Reviewed-by:
Roland Scheidegger <sroland@vmware.com> (cherry picked from commit d84b85bc)