Merge branch 'net_sched-reflect-tx_queue_len-change-for-pfifo_fast'

Cong Wang says:

====================
net_sched: reflect tx_queue_len change for pfifo_fast

This pathcset restores the pfifo_fast qdisc behavior of dropping
packets based on latest dev->tx_queue_len. Patch 1 introduces
a helper, patch 2 introduces a new Qdisc ops which is called when
we modify tx_queue_len, patch 3 implements this ops for pfifo_fast.

Please see each patch for details.

---
v3: use skb_array_resize_multiple()
v2: handle error case for ->change_tx_queue_len()
====================

Signed-off-by: David S. Miller <davem@davemloft.net>