drm/i915: Only ignore eDP ports that are connected

drm/i915: Only ignore eDP ports that are connected

If the VBT says that a certain port should be eDP (and hence fused off
from HDMI), but in reality it isn't, we need to try and acquire the HDMI
connection instead. So only trust the VBT edp setting if we can connect
to an eDP device on that port.

Fixes: a1fb43a6ce (drm/i915: Don't register HDMI connectors for eDP ports on VLV/CHV)
References: https://bugs.freedesktop.org/show_bug.cgi?id=96288
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Tested-by: Phidias Chiang <phidias.chiang@canonical.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1464766070-31623-1-git-send-email-chris@chris-wilson.co.uk
(cherry picked from commit 457c52d87e5dac9a4cf1a6a287e60ea7645067d4)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>