Adds a new qdisc operation dump_stats which qdiscs can use
to dump statistics. The op is invoked between gnet_stats_start_copy
and gnet_stats_finish_copy and therefore stats_lock is already
held. This is required to ensure proper locking throughout the
whole statistic dumping procedure.
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>