net_sched: sch_fq: remove q->ktime_cache

net_sched: sch_fq: remove q->ktime_cache

Now that both enqueue() and dequeue() need to use ktime_get_ns(),
there is no point wasting 8 bytes in struct fq_sched_data.

This makes room for future fields. ;)

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>