i965/gen7: Emit workaround flush when changing GS enable state.
v2: Don't go to extra work to avoid extraneous flushes. (Previous experiments in the kernel have suggested that flushing the pipeline when it is already empty is extremely cheap). Cc: "10.0" <firstname.lastname@example.org> Reviewed-by: Eric Anholt <email@example.com>
Showing with 72 additions and 22 deletions