drm: minor kref_put() nits

There's no need to pass kref_put() the address of a function (just the
function will do just fine) nor to cast its unused return to void.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/gpu/drm/ttm/ttm_object.c

@@ -206,7 +206,7 @@ void ttm_base_object_unref(struct ttm_base_object **p_base)
 	 */
 
 	write_lock(&tdev->object_lock);
-	(void)kref_put(&base->refcount, &ttm_release_base);
+	kref_put(&base->refcount, ttm_release_base);
 	write_unlock(&tdev->object_lock);
 }
 EXPORT_SYMBOL(ttm_base_object_unref);