drm/i915: clean up backlight conditional build

I've always felt the backlight device conditional build has been all
backwards. Make it feel right.

Gently move things towards connector based stuff while at it.

There should be no functional changes.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 1e49aa8..5548180 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -808,7 +808,7 @@
 int intel_panel_setup_backlight(struct drm_connector *connector);
 void intel_panel_enable_backlight(struct intel_connector *connector);
 void intel_panel_disable_backlight(struct intel_connector *connector);
-void intel_panel_destroy_backlight(struct drm_device *dev);
+void intel_panel_destroy_backlight(struct drm_connector *connector);
 enum drm_connector_status intel_panel_detect(struct drm_device *dev);