tcm_fc: using kfree_rcu() to simplify the code

The callback function of call_rcu() just calls a kfree(), so we
can use kfree_rcu() instead of call_rcu() + callback function.
Signed-off-by: NWei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: NNicholas Bellinger <nab@linux-iscsi.org>

drivers/target/tcm_fc/tfc_sess.c

@@ -428,19 +428,12 @@ static int ft_prli(struct fc_rport_priv *rdata, u32 spp_len,
 	return ret;
 }
 
-static void ft_sess_rcu_free(struct rcu_head *rcu)
-{
-	struct ft_sess *sess = container_of(rcu, struct ft_sess, rcu);
-
-	kfree(sess);
-}
-
 static void ft_sess_free(struct kref *kref)
 {
 	struct ft_sess *sess = container_of(kref, struct ft_sess, kref);
 
 	transport_deregister_session(sess->se_sess);
-	call_rcu(&sess->rcu, ft_sess_rcu_free);
+	kfree_rcu(sess, rcu);
 }
 
 void ft_sess_put(struct ft_sess *sess)