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/ipv6/raw.c

@@ -130,14 +130,14 @@ static mh_filter_t __rcu *mh_filter __read_mostly;
 
 int rawv6_mh_filter_register(mh_filter_t filter)
 {
-	rcu_assign_pointer(mh_filter, filter);
+	RCU_INIT_POINTER(mh_filter, filter);
 	return 0;
 }
 EXPORT_SYMBOL(rawv6_mh_filter_register);
 
 int rawv6_mh_filter_unregister(mh_filter_t filter)
 {
-	rcu_assign_pointer(mh_filter, NULL);
+	RCU_INIT_POINTER(mh_filter, NULL);
 	synchronize_rcu();
 	return 0;
 }