drm/i915: Don't register HDMI connectors for eDP ports on VLV/CHV

If we determine that a specific port is eDP, don't register the HDMI
connector/encoder for it. The reason being that we want to disable
HPD interrupts for eDP ports when the display is off, but the presence
of the extra HDMI connector would demand the HPD interrupt to remain
enabled all the time.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>