Fixes KHR-GL45.shader_ballot_tests.ShaderBallotAvailability, which
causes some silly swizzles to appear, triggering this optimization to
get hit.
Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Cc: mesa-stable@lists.freedesktop.org