tcm_fc: rcu_deref outside rcu lock/unlock section

Use rcu_dereference_protected in order to prevent lockdep
complaint. Sequel of the patch 863555be

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Denis Efremov <yefremov.denis@gmail.com>
Acked-by: Mark D. Rustad <mark.d.rustad@intel.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/target/tcm_fc/tfc_sess.c b/drivers/target/tcm_fc/tfc_sess.c
index 87901fa..3c9e5b5 100644
--- a/drivers/target/tcm_fc/tfc_sess.c
+++ b/drivers/target/tcm_fc/tfc_sess.c
@@ -456,7 +456,9 @@
 	struct ft_tport *tport;
 
 	mutex_lock(&ft_lport_lock);
-	tport = rcu_dereference(rdata->local_port->prov[FC_TYPE_FCP]);
+	tport = rcu_dereference_protected(rdata->local_port->prov[FC_TYPE_FCP],
+					  lockdep_is_held(&ft_lport_lock));
+
 	if (!tport) {
 		mutex_unlock(&ft_lport_lock);
 		return;