net: sched: avoid writing on noop_qdisc

While noop_qdisc.gso_skb and noop_qdisc.skb_bad_txq are not used
in other places, it seems not correct to overwrite their fields
in dev_init_scheduler_queue().

noop_qdisc is essentially a shared and read-only object, even if
it is not marked as const because of some implementation detail.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>