RDMA/nldev: Skip counter if port doesn't match

The counter resource should return -EAGAIN if it was requested for a
different port, this is similar to how QP works if the users provides a
port filter.

Otherwise port filtering in netlink will return broken counter nests.

Fixes: c4ffee7c9b ("RDMA/netlink: Implement counter dumpit calback")
Link: https://lore.kernel.org/r/20191020062800.8065-1-leon@kernel.org
Signed-off-by: Mark Zhang <markz@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/nldev.c

@@ -778,7 +778,7 @@ static int fill_res_counter_entry(struct sk_buff *msg, bool has_cap_net_admin,
 		container_of(res, struct rdma_counter, res);
 
 	if (port && port != counter->port)
-		return 0;
+		return -EAGAIN;
 
 	/* Dump it even query failed */
 	rdma_counter_query_stats(counter);