sch_cbq: remove unnecessary null pointer check

It already has a NULL pointer check of rtab in qdisc_put_rtab().
Remove the check outside of qdisc_put_rtab().
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sched/sch_cbq.c

@@ -1783,8 +1783,7 @@ cbq_change_class(struct Qdisc *sch, u32 classid, u32 parentid, struct nlattr **t
 						    qdisc_root_sleeping_lock(sch),
 						    tca[TCA_RATE]);
 			if (err) {
-				if (rtab)
-					qdisc_put_rtab(rtab);
+				qdisc_put_rtab(rtab);
 				return err;
 			}
 		}