drm/atomic: Pass connector and state to update_connector_routing.

Minor cleanup, connector and connector_state are always non-NULL here.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1456303053-28806-3-git-send-email-maarten.lankhorst@linux.intel.com