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/802/stp.c

@@ -88,9 +88,9 @@ void stp_proto_unregister(const struct stp_proto *proto)
 {
 	mutex_lock(&stp_proto_mutex);
 	if (is_zero_ether_addr(proto->group_address))
-		rcu_assign_pointer(stp_proto, NULL);
+		RCU_INIT_POINTER(stp_proto, NULL);
 	else
-		rcu_assign_pointer(garp_protos[proto->group_address[5] -
+		RCU_INIT_POINTER(garp_protos[proto->group_address[5] -
 					       GARP_ADDR_MIN], NULL);
 	synchronize_rcu();