drm/i915: Get rid of unused transitional members.

The previous commit converted hw readout to atomic, all the new_*
members were used for restoring the old state, but with the
conversion of suspend to atomic there's no use left for them.

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