net: minor optimization in qdisc_qstats_cpu_drop()

per_cpu_inc() is faster (at least on x86) than per_cpu_ptr(xxx)++;
Signed-off-by: NEric Dumazet <edumazet@google.com>
Acked-by: NJohn Fastabend <john.r.fastabend@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/sch_generic.h

@@ -592,7 +592,7 @@ static inline void qdisc_qstats_drop(struct Qdisc *sch)
 
 static inline void qdisc_qstats_cpu_drop(struct Qdisc *sch)
 {
-	qstats_drop_inc(this_cpu_ptr(sch->cpu_qstats));
+	this_cpu_inc(sch->cpu_qstats->drops);
 }
 
 static inline void qdisc_qstats_overlimit(struct Qdisc *sch)