taprio: Fix dropping packets when using taprio + ETF offloading

When using taprio offloading together with ETF offloading, configured
like this, for example:

$ tc qdisc replace dev $IFACE parent root handle 100 taprio \
  	num_tc 4 \
        map 2 2 1 0 3 2 2 2 2 2 2 2 2 2 2 2 \
	queues 1@0 1@1 1@2 1@3 \
	base-time $BASE_TIME \
	sched-entry S 01 1000000 \
	sched-entry S 0e 1000000 \
	flags 0x2

$ tc qdisc replace dev $IFACE parent 100:1 etf \
     	offload delta 300000 clockid CLOCK_TAI

During enqueue, it works out that the verification added for the
"txtime" assisted mode is run when using taprio + ETF offloading, the
only thing missing is initializing the 'next_txtime' of all the cycle
entries. (if we don't set 'next_txtime' all packets from SO_TXTIME
sockets are dropped)

Fixes: 4cfd5779 ("taprio: Add support for txtime-assist mode")
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_taprio.c

@@ -1522,9 +1522,9 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
 		goto unlock;
 	}
 
-	if (TXTIME_ASSIST_IS_ENABLED(q->flags)) {
 	setup_txtime(q, new_admin, start);
 
+	if (TXTIME_ASSIST_IS_ENABLED(q->flags)) {
 		if (!oper) {
 			rcu_assign_pointer(q->oper_sched, new_admin);
 			err = 0;