net_sched: sch_fq: add TCA_FQ_WEIGHTS attribute

This attribute can be used to tune the per band weight
and report them in "tc qdisc show" output:

qdisc fq 802f: parent 1:9 limit 100000p flow_limit 500p buckets 1024 orphan_mask 1023
 quantum 8364b initial_quantum 41820b low_rate_threshold 550Kbit
 refill_delay 40ms timer_slack 10us horizon 10s horizon_drop
 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1 weights 589824 196608 65536
 Sent 236460814 bytes 792991 pkt (dropped 0, overlimits 0 requeues 0)
 rate 25816bit 10pps backlog 0b 0p requeues 0
  flows 4 (inactive 4 throttled 0)
  gc 0 throttled 19 latency 17.6us fastpath 773882

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Dave Taht <dave.taht@gmail.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>