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>

net/ipv6/addrconf.c

@@ -428,7 +428,7 @@ static struct inet6_dev * ipv6_add_dev(struct net_device *dev)
 	ndev->tstamp = jiffies;
 	addrconf_sysctl_register(ndev);
 	/* protected by rtnl_lock */
-	rcu_assign_pointer(dev->ip6_ptr, ndev);
+	RCU_INIT_POINTER(dev->ip6_ptr, ndev);
 
 	/* Join all-node multicast group */
 	ipv6_dev_mc_inc(dev, &in6addr_linklocal_allnodes);
@@ -2733,7 +2733,7 @@ static int addrconf_ifdown(struct net_device *dev, int how)
 		idev->dead = 1;
 
 		/* protected by rtnl_lock */
-		rcu_assign_pointer(dev->ip6_ptr, NULL);
+		RCU_INIT_POINTER(dev->ip6_ptr, NULL);
 
 		/* Step 1.5: remove snmp6 entry */
 		snmp6_unregister_dev(idev);