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/ipv4/gre.c b/net/ipv4/gre.c
index dbfc21d..8cb1ebb 100644
--- a/net/ipv4/gre.c
+++ b/net/ipv4/gre.c
@@ -34,7 +34,7 @@
 	if (gre_proto[version])
 		goto err_out_unlock;
 
-	rcu_assign_pointer(gre_proto[version], proto);
+	RCU_INIT_POINTER(gre_proto[version], proto);
 	spin_unlock(&gre_proto_lock);
 	return 0;
 
@@ -54,7 +54,7 @@
 	if (rcu_dereference_protected(gre_proto[version],
 			lockdep_is_held(&gre_proto_lock)) != proto)
 		goto err_out_unlock;
-	rcu_assign_pointer(gre_proto[version], NULL);
+	RCU_INIT_POINTER(gre_proto[version], NULL);
 	spin_unlock(&gre_proto_lock);
 	synchronize_rcu();
 	return 0;