drm/i915: add attached connector to hdmi container

This patch adds the intel_connector initialized to intel_hdmi
display, during the init phase, just like the other encoders do.
This attachment is very useful when we need to extract the connector
pointer during the hotplug handler function

Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>