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/ibss.c b/net/mac80211/ibss.c
index 56c24ca..4f9235b 100644
--- a/net/mac80211/ibss.c
+++ b/net/mac80211/ibss.c
@@ -84,7 +84,7 @@
 	drv_reset_tsf(local);
 
 	skb = ifibss->skb;
-	rcu_assign_pointer(ifibss->presp, NULL);
+	RCU_INIT_POINTER(ifibss->presp, NULL);
 	synchronize_rcu();
 	skb->data = skb->head;
 	skb->len = 0;
@@ -184,7 +184,7 @@
 		*pos++ = 0; /* U-APSD no in use */
 	}
 
-	rcu_assign_pointer(ifibss->presp, skb);
+	RCU_INIT_POINTER(ifibss->presp, skb);
 
 	sdata->vif.bss_conf.beacon_int = beacon_int;
 	sdata->vif.bss_conf.basic_rates = basic_rates;
@@ -995,7 +995,7 @@
 	kfree(sdata->u.ibss.ie);
 	skb = rcu_dereference_protected(sdata->u.ibss.presp,
 					lockdep_is_held(&sdata->u.ibss.mtx));
-	rcu_assign_pointer(sdata->u.ibss.presp, NULL);
+	RCU_INIT_POINTER(sdata->u.ibss.presp, NULL);
 	sdata->vif.bss_conf.ibss_joined = false;
 	ieee80211_bss_info_change_notify(sdata, BSS_CHANGED_BEACON_ENABLED |
 						BSS_CHANGED_IBSS);