drm/i915: Create generic intel_panel for LVDS and eDP

Create a generic struct intel_panel for sharing a data structure and code
between eDP and LVDS panels. Add the new struct to intel_connector so that
later on we can have generic EDID and mode reading functions with EDID
caching that transparently fallback to fixed mode when EDID is not
available.

Add intel_panel as a dummy first, and move data (such as the mentioned
fixed mode) to it in later patches.

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>
[danvet: Fixup tiny conflict in intel_dp_destroy.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c
index 6435bf3..6b31e25 100644
--- a/drivers/gpu/drm/i915/intel_lvds.c
+++ b/drivers/gpu/drm/i915/intel_lvds.c
@@ -554,6 +554,7 @@
 		acpi_lid_notifier_unregister(&lvds_connector->lid_notifier);
 
 	intel_panel_destroy_backlight(connector->dev);
+	intel_panel_fini(&lvds_connector->base.panel);
 
 	drm_sysfs_connector_remove(connector);
 	drm_connector_cleanup(connector);
@@ -1106,6 +1107,7 @@
 	}
 	drm_sysfs_connector_add(connector);
 
+	intel_panel_init(&intel_connector->panel);
 	intel_panel_setup_backlight(connector);
 
 	return true;