net: rtnetlink: convert rcu_assign_pointer to RCU_INIT_POINTER

It no need barrier when assigning a NULL value to an RCU protected
pointer. So use RCU_INIT_POINTER() instead for more fast.
Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/rtnetlink.c

@@ -301,7 +301,7 @@ int rtnl_unregister(int protocol, int msgtype)
 	}
 
 	link = rtnl_dereference(tab[msgindex]);
-	rcu_assign_pointer(tab[msgindex], NULL);
+	RCU_INIT_POINTER(tab[msgindex], NULL);
 	rtnl_unlock();
 
 	kfree_rcu(link, rcu);
@@ -337,7 +337,7 @@ void rtnl_unregister_all(int protocol)
 		if (!link)
 			continue;
 
-		rcu_assign_pointer(tab[msgindex], NULL);
+		RCU_INIT_POINTER(tab[msgindex], NULL);
 		kfree_rcu(link, rcu);
 	}
 	rtnl_unlock();