rcu: convert uses of rcu_assign_pointer(x, NULL) to RCU_INIT_POINTER

When assigning a NULL value to an RCU protected pointer, no barrier
is needed. The rcu_assign_pointer, used to handle that but will soon
change to not handle the special case.

Convert all rcu_assign_pointer of NULL value.

//smpl
@@ expression P; @@

- rcu_assign_pointer(P, NULL)
+ RCU_INIT_POINTER(P, NULL)

// </smpl>

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/phonet/af_phonet.c b/net/phonet/af_phonet.c
index c6fffd9..bf10ea8 100644
--- a/net/phonet/af_phonet.c
+++ b/net/phonet/af_phonet.c
@@ -480,7 +480,7 @@
 	if (proto_tab[protocol])
 		err = -EBUSY;
 	else
-		rcu_assign_pointer(proto_tab[protocol], pp);
+		RCU_INIT_POINTER(proto_tab[protocol], pp);
 	mutex_unlock(&proto_tab_lock);
 
 	return err;
@@ -491,7 +491,7 @@
 {
 	mutex_lock(&proto_tab_lock);
 	BUG_ON(proto_tab[protocol] != pp);
-	rcu_assign_pointer(proto_tab[protocol], NULL);
+	RCU_INIT_POINTER(proto_tab[protocol], NULL);
 	mutex_unlock(&proto_tab_lock);
 	synchronize_rcu();
 	proto_unregister(pp->prot);