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/core/dev.c b/net/core/dev.c
index 17d67b5..9428766 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3094,8 +3094,8 @@
 {
 
 	ASSERT_RTNL();
-	rcu_assign_pointer(dev->rx_handler, NULL);
-	rcu_assign_pointer(dev->rx_handler_data, NULL);
+	RCU_INIT_POINTER(dev->rx_handler, NULL);
+	RCU_INIT_POINTER(dev->rx_handler_data, NULL);
 }
 EXPORT_SYMBOL_GPL(netdev_rx_handler_unregister);