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: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>