drm/i915/lvds: Move some connector specific info across from the encoder

As there is 1:1 mapping between encoder and connector for the LVDS, the
goal is to simply reduce the amount of noise within the connector
functions, i.e. we split the encoder/connector for LVDS as best we can and
try to only operate on the LVDS connector from the connector funcs and the
LVDS encoder form the encoder funcs.

Based on earlier work by Chris Wilson <chris@chris-wilson.co.uk>

CC: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>