aufs: bugfix, no nested RCU for kfree()

Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>
(cherry picked from commit 4596850541ed7144f7fea951d02f0f6251c4a997)

fs/aufs/dynop.c

@@ -101,7 +101,7 @@ static void dy_free_rcu(struct rcu_head *rcu)
 
 	key = container_of(rcu, struct au_dykey, dk_rcu);
 	DyPrSym(key);
-	au_kfree_rcu(key);
+	kfree(key);
 }
 
 static void dy_free(struct kref *kref)