drm/i915: Set csc coefficients in update_pipe_size.

This might not have been set during boot, and when we preserve
the initial mode this can result in a black screen.

Cc: Daniel Stone <daniels@collabora.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>