ACPI / video: Make acpi_video_unregister_backlight() private

acpi_video_unregister_backlight() is now only used by video_detect.c
which is part of the same acpi_video module as video.c, make
acpi_video_unregister_backlight() private to this module.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Darren Hart <dvhart@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/acpi_video.c

@@ -2021,7 +2021,6 @@ void acpi_video_unregister_backlight(void)
 	}
 	mutex_unlock(&register_count_mutex);
 }
-EXPORT_SYMBOL(acpi_video_unregister_backlight);
 
 /*
  * This is kind of nasty. Hardware using Intel chipsets may require

drivers/acpi/video_detect.c

@@ -37,6 +37,8 @@
 ACPI_MODULE_NAME("video");
 #define _COMPONENT		ACPI_VIDEO_COMPONENT
 
+void acpi_video_unregister_backlight(void);
+
 static bool backlight_notifier_registered;
 static struct notifier_block backlight_nb;
 

include/acpi/video.h

@@ -27,7 +27,6 @@ enum acpi_backlight_type {
 #if (defined CONFIG_ACPI_VIDEO || defined CONFIG_ACPI_VIDEO_MODULE)
 extern int acpi_video_register(void);
 extern void acpi_video_unregister(void);
-extern void acpi_video_unregister_backlight(void);
 extern int acpi_video_get_edid(struct acpi_device *device, int type,
 			       int device_id, void **edid);
 extern enum acpi_backlight_type acpi_video_get_backlight_type(void);
@@ -35,7 +34,6 @@ extern void acpi_video_set_dmi_backlight_type(enum acpi_backlight_type type);
 #else
 static inline int acpi_video_register(void) { return 0; }
 static inline void acpi_video_unregister(void) { return; }
-static inline void acpi_video_unregister_backlight(void) { return; }
 static inline int acpi_video_get_edid(struct acpi_device *device, int type,
 				      int device_id, void **edid)
 {