drm/i915: LVDS fallback to fixed-mode if EDID not present

Use the recorded panel fixed-mode to populate the get_modes() request in
the absence of an EDID.

Fixes regression from
commit 9cd300e038d492af4990b04e127e0bd2df64b1ca
Author: Jani Nikula <jani.nikula@intel.com>
Date:   Fri Oct 19 14:51:52 2012 +0300

    drm/i915: Move cached EDID to intel_connector

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
[danvet: Drop the retval-changing hunk, as suggested by Jani in his
review and acked by Chris.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_lvds.c

@@ -460,13 +460,8 @@ static int intel_lvds_get_modes(struct drm_connector *connector)
 	struct drm_display_mode *mode;
 
 	/* use cached edid if we have one */
-	if (lvds_connector->base.edid) {
-		/* invalid edid */
-		if (IS_ERR(lvds_connector->base.edid))
-			return 0;
-
+	if (!IS_ERR_OR_NULL(lvds_connector->base.edid))
 		return drm_add_edid_modes(connector, lvds_connector->base.edid);
-	}
 
 	mode = drm_mode_duplicate(dev, lvds_connector->base.panel.fixed_mode);
 	if (mode == NULL)