bql: Byte queue limits

Networking stack support for byte queue limits, uses dynamic queue
limits library.  Byte queue limits are maintained per transmit queue,
and a dql structure has been added to netdev_queue structure for this
purpose.

Configuration of bql is in the tx-<n> sysfs directory for the queue
under the byte_queue_limits directory.  Configuration includes:
limit_min, bql minimum limit
limit_max, bql maximum limit
hold_time, bql slack hold time

Also under the directory are:
limit, current byte limit
inflight, current number of bytes on the queue

Signed-off-by: Tom Herbert <therbert@google.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/dev.c b/net/core/dev.c
index cb8f753..91a5991 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5470,6 +5470,9 @@
 	queue->xmit_lock_owner = -1;
 	netdev_queue_numa_node_write(queue, NUMA_NO_NODE);
 	queue->dev = dev;
+#ifdef CONFIG_BQL
+	dql_init(&queue->dql, HZ);
+#endif
 }
 
 static int netif_alloc_netdev_queues(struct net_device *dev)