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/netfilter/nfnetlink.c

diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c
index 1905976..c879c1a 100644
--- a/net/netfilter/nfnetlink.c
+++ b/net/netfilter/nfnetlink.c
@@ -59,7 +59,7 @@
 		nfnl_unlock();
 		return -EBUSY;
 	}
-	rcu_assign_pointer(subsys_table[n->subsys_id], n);
+	RCU_INIT_POINTER(subsys_table[n->subsys_id], n);
 	nfnl_unlock();
 
 	return 0;
@@ -210,7 +210,7 @@
 	if (!nfnl)
 		return -ENOMEM;
 	net->nfnl_stash = nfnl;
-	rcu_assign_pointer(net->nfnl, nfnl);
+	RCU_INIT_POINTER(net->nfnl, nfnl);
 	return 0;
 }
 
@@ -219,7 +219,7 @@
 	struct net *net;
 
 	list_for_each_entry(net, net_exit_list, exit_list)
-		rcu_assign_pointer(net->nfnl, NULL);
+		RCU_INIT_POINTER(net->nfnl, NULL);
 	synchronize_net();
 	list_for_each_entry(net, net_exit_list, exit_list)
 		netlink_kernel_release(net->nfnl_stash);