IB/cm: Remove now useless rcu_lock in dst_fetch_ha

This lock used to be protecting a call to dst_get_neighbour_noref,
however the below commit changed it to dst_neigh_lookup which no longer
requires rcu.

Access to nud_state, neigh_event_send or rdma_copy_addr does not require
RCU, so delete the lock.

Fixes: 02b61955 ("infiniband: Convert dst_fetch_ha() over to dst_neigh_lookup().")
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>

drivers/infiniband/core/addr.c

@@ -315,19 +315,17 @@ static int dst_fetch_ha(const struct dst_entry *dst,
 	int ret = 0;
 
 	n = dst_neigh_lookup(dst, daddr);
+	if (!n)
+		return -ENODATA;
 
-	rcu_read_lock();
-	if (!n || !(n->nud_state & NUD_VALID)) {
-		if (n)
-			neigh_event_send(n, NULL);
+	if (!(n->nud_state & NUD_VALID)) {
+		neigh_event_send(n, NULL);
 		ret = -ENODATA;
 	} else {
 		rdma_copy_addr(dev_addr, dst->dev, n->ha);
 	}
-	rcu_read_unlock();
 
-	if (n)
-		neigh_release(n);
+	neigh_release(n);
 
 	return ret;
 }