ipv6: remove a rcu_read_lock in ndisc_constructor

in6_dev_get(dev) takes a reference on struct inet6_dev, we dont need
rcu locking in ndisc_constructor()

Signed-off-by: Roy.Li <rongqing.li@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ndisc.c

@@ -370,17 +370,14 @@ static int ndisc_constructor(struct neighbour *neigh)
 	struct neigh_parms *parms;
 	int is_multicast = ipv6_addr_is_multicast(addr);
 
-	rcu_read_lock();
 	in6_dev = in6_dev_get(dev);
 	if (in6_dev == NULL) {
-		rcu_read_unlock();
 		return -EINVAL;
 	}
 
 	parms = in6_dev->nd_parms;
 	__neigh_parms_put(neigh->parms);
 	neigh->parms = neigh_parms_clone(parms);
-	rcu_read_unlock();
 
 	neigh->type = is_multicast ? RTN_MULTICAST : RTN_UNICAST;
 	if (!dev->header_ops) {