Merge remote-tracking branch 'stefanha/net' into staging

# By Jason Wang (2) and others
# Via Stefan Hajnoczi
* stefanha/net:
  qmp: netdev_add is like -netdev, not -net, fix documentation
  doc: document -netdev hubport
  net: reduce the unnecessary memory allocation of multiqueue
  tap: set IFF_ONE_QUEUE per default
  tap: forbid creating multiqueue tap when hub is used
  net: fix unbounded NetQueue
  net: fix qemu_flush_queued_packets() in presence of a hub