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/mac80211/cfg.c b/net/mac80211/cfg.c
index 3d1b091..86f8f49 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -62,7 +62,7 @@
 
 	if (type == NL80211_IFTYPE_AP_VLAN &&
 	    params && params->use_4addr == 0)
-		rcu_assign_pointer(sdata->u.vlan.sta, NULL);
+		RCU_INIT_POINTER(sdata->u.vlan.sta, NULL);
 	else if (type == NL80211_IFTYPE_STATION &&
 		 params && params->use_4addr >= 0)
 		sdata->u.mgd.use_4addr = params->use_4addr;
@@ -542,7 +542,7 @@
 
 	sdata->vif.bss_conf.dtim_period = new->dtim_period;
 
-	rcu_assign_pointer(sdata->u.ap.beacon, new);
+	RCU_INIT_POINTER(sdata->u.ap.beacon, new);
 
 	synchronize_rcu();
 
@@ -594,7 +594,7 @@
 	if (!old)
 		return -ENOENT;
 
-	rcu_assign_pointer(sdata->u.ap.beacon, NULL);
+	RCU_INIT_POINTER(sdata->u.ap.beacon, NULL);
 	synchronize_rcu();
 	kfree(old);
 
@@ -857,7 +857,7 @@
 				return -EBUSY;
 			}
 
-			rcu_assign_pointer(vlansdata->u.vlan.sta, sta);
+			RCU_INIT_POINTER(vlansdata->u.vlan.sta, sta);
 		}
 
 		sta->sdata = vlansdata;