drm/i915: Pass connector state to intel_panel_set_backlight_acpi

Passing the state is also needed to convert the backlight functions
to use the correct state instead of looking it up.

This is done as a separate commit to allow easier bisecting.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100022
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170612102115.23665-3-maarten.lankhorst@linux.intel.com
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

drivers/gpu/drm/i915/intel_drv.h

@@ -1712,7 +1712,7 @@ void intel_pch_panel_fitting(struct intel_crtc *crtc,
 void intel_gmch_panel_fitting(struct intel_crtc *crtc,
 			      struct intel_crtc_state *pipe_config,
 			      int fitting_mode);
-void intel_panel_set_backlight_acpi(struct intel_connector *connector,
+void intel_panel_set_backlight_acpi(const struct drm_connector_state *conn_state,
 				    u32 level, u32 max);
 int intel_panel_setup_backlight(struct drm_connector *connector,
 				enum pipe pipe);