Set required clock gating and chicken bits on VLV.

v2: set PIXEL_SUBSPAN_COLLECT_OPT_DISABLE too (Ben)
    move function below ivb version to pretend to be consistent (Ben)
Reviewed-by: NBen Widawsky <ben@bwidawsk.net>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>