drm/i915: Move registration actions to connector->late_register

With the introduction of a connector->func for callback from
drm_connector_register() we can move all the tasks that we want to do
upon registration into that callback. Later, this will allow us to
reorder the registration and defer it until after the device is setup
and ready for userspace.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1466773227-7994-2-git-send-email-chris@chris-wilson.co.uk