net_sched: sch_fq: add the ability to offload pacing

net_sched: sch_fq: add the ability to offload pacing

Some network devices have the ability to offload EDT (Earliest
Departure Time) which is the model used for TCP pacing and FQ packet
scheduler.

Some of them implement the timing wheel mechanism described in
https://saeed.github.io/files/carousel-sigcomm17.pdf
with an associated 'timing wheel horizon'.

This patchs adds to FQ packet scheduler TCA_FQ_OFFLOAD_HORIZON
attribute.

Its value is capped by the device max_pacing_offload_horizon,
added in the prior patch.

It allows FQ to let packets within pacing offload horizon
to be delivered to the device, which will handle the needed
delay without host involvement.

Signed-off-by: Jeffrey Ji <jeffreyji@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20241003121219.2396589-3-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>