pkt_sched: sch_qfq: remove unused member of struct qfq_sched

The member (u32) "num_active_agg" of struct qfq_sched has been unused
since its introduction in 462dbc91
"pkt_sched: QFQ Plus: fair-queueing service at DRR cost" and (AFAICT)
there is no active plan to use it; this removes the member.
Signed-off-by: NAndrea Parri <parri.andrea@gmail.com>
Acked-by: NPaolo Valente <paolo.valente@unimore.it>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sched/sch_qfq.c

@@ -186,7 +186,6 @@ struct qfq_sched {
 
 	u64			oldV, V;	/* Precise virtual times. */
 	struct qfq_aggregate	*in_serv_agg;   /* Aggregate being served. */
-	u32			num_active_agg; /* Num. of active aggregates */
 	u32			wsum;		/* weight sum */
 	u32			iwsum;		/* inverse weight sum */