drm: also move DSI panels to the front of the connector list

We've overlooked adding DSI panels to the front of the connector
list. This seems to be the right thing to do, and I suspect this might
fix some issues, although I currently have no evidence to support this.

v2: also git add the comment change

Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1479378548-32695-1-git-send-email-jani.nikula@intel.com