net: sched: drop all special handling of tx_queue_len == 0

Those were all workarounds for the formerly double meaning of
tx_queue_len, which broke scheduling algorithms if untreated.

Now that all in-tree drivers have been converted away from setting
tx_queue_len = 0, it should be safe to drop these workarounds for
categorically broken setups.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/sch_plug.c b/net/sched/sch_plug.c
index ade9445..5abfe44 100644
--- a/net/sched/sch_plug.c
+++ b/net/sched/sch_plug.c
@@ -130,12 +130,8 @@
 	q->unplug_indefinite = false;
 
 	if (opt == NULL) {
-		/* We will set a default limit of 100 pkts (~150kB)
-		 * in case tx_queue_len is not available. The
-		 * default value is completely arbitrary.
-		 */
-		u32 pkt_limit = qdisc_dev(sch)->tx_queue_len ? : 100;
-		q->limit = pkt_limit * psched_mtu(qdisc_dev(sch));
+		q->limit = qdisc_dev(sch)->tx_queue_len
+		           * psched_mtu(qdisc_dev(sch));
 	} else {
 		struct tc_plug_qopt *ctl = nla_data(opt);