drm: remove second forward decleration of drm device struct.

Signed-off-by: Dave Airlie <airlied@linux.ie>
diff --git a/drivers/char/drm/drmP.h b/drivers/char/drm/drmP.h
index 9dd0760..dde02a1 100644
--- a/drivers/char/drm/drmP.h
+++ b/drivers/char/drm/drmP.h
@@ -559,8 +559,6 @@
  * a family of cards. There will one drm_device for each card present
  * in this family
  */
-struct drm_device;
-
 struct drm_driver {
 	int (*load) (struct drm_device *, unsigned long flags);
 	int (*firstopen) (struct drm_device *);