RDMA/nldev: Don't expose number of not-visible entries

Netlink dumpit handshake exchanges the index from which kernel should
start to return its value, in current code, this index included
not-visible in this PID items too and indirectly revealed the number of
entries.
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/nldev.c

@@ -1123,13 +1123,10 @@ static int res_get_common_dumpit(struct sk_buff *skb,
 	 * objects.
 	 */
 	xa_for_each(&rt->xa, id, res) {
-		if (idx < start)
-			goto next;
-
 		if (!is_visible_in_pid_ns(res))
-			goto next;
+			continue;
 
-		if (!rdma_restrack_get(res))
+		if (idx < start || !rdma_restrack_get(res))
 			goto next;
 
 		xa_unlock(&rt->xa);