drm/crtc-helper: gc usless connector loop in disable_unused_functions

I've forgotten to clean this all up correctly in

commit e3d6ddb3
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Tue Apr 1 22:15:00 2014 +0200

    drm/crtc-helper: don't disable disconnected outputs

Reported-by: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>