drm: move drm vblank initialization/cleanup to driver load/unload

drm vblank initialization keeps track of the changes in driver-supplied
frame counts across vt switch and mode setting, but only if you let it by
not tearing down the drm vblank structure.

Signed-off-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 28c7f16..d5e8e5c 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -1151,6 +1151,7 @@
 extern void drm_handle_vblank(struct drm_device *dev, int crtc);
 extern int drm_vblank_get(struct drm_device *dev, int crtc);
 extern void drm_vblank_put(struct drm_device *dev, int crtc);
+extern void drm_vblank_cleanup(struct drm_device *dev);
 /* Modesetting support */
 extern int drm_modeset_ctl(struct drm_device *dev, void *data,
 			   struct drm_file *file_priv);