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/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index 0256b8a..d0a42df 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -2927,7 +2927,7 @@
 	if (nlsk == NULL)
 		return -ENOMEM;
 	net->xfrm.nlsk_stash = nlsk; /* Don't set to NULL */
-	rcu_assign_pointer(net->xfrm.nlsk, nlsk);
+	RCU_INIT_POINTER(net->xfrm.nlsk, nlsk);
 	return 0;
 }
 
@@ -2935,7 +2935,7 @@
 {
 	struct net *net;
 	list_for_each_entry(net, net_exit_list, exit_list)
-		rcu_assign_pointer(net->xfrm.nlsk, NULL);
+		RCU_INIT_POINTER(net->xfrm.nlsk, NULL);
 	synchronize_net();
 	list_for_each_entry(net, net_exit_list, exit_list)
 		netlink_kernel_release(net->xfrm.nlsk_stash);