drm/i915: load the LUT before pipe enable on ILK+

Per the specs and to address
https://bugs.freedesktop.org/show_bug.cgi?id=36888

.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: stable@kernel.org
Signed-off-by: Keith Packard <keithp@keithp.com>