pkt_sched: sch_sfq: dump a real number of flows

Dump the "flows" number according to the number of active flows
instead of repeating the "limit".

Reported-by: Denys Fedoryshchenko <denys@visp.net.lb>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>