drm/i915: Unregister ACPI video driver when exiting

The i915 DRM triggers registration of the ACPI video driver on load. It
should unregister it at unload in order to avoid generating backtraces on
being reloaded.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Eric Anholt <eric@anholt.net>

include/acpi/video.h

@@ -3,8 +3,10 @@
 
 #if (defined CONFIG_ACPI_VIDEO || defined CONFIG_ACPI_VIDEO_MODULE)
 extern int acpi_video_register(void);
+extern int acpi_video_exit(void);
 #else
 static inline int acpi_video_register(void) { return 0; }
+static inline void acpi_video_exit(void) { return; }
 #endif
 
 #endif