net_sched: red: Avoid devision by zero

Do not allow delta value to be zero since it is used as a divisor.

Fixes: 8af2a218de38 ("sch_red: Adaptative RED AQM")
Signed-off-by: Nogah Frankel <nogahf@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/red.h

@@ -179,7 +179,7 @@ static inline void red_set_parms(struct red_parms *p,
 	p->qth_max	= qth_max << Wlog;
 	p->Wlog		= Wlog;
 	p->Plog		= Plog;
-	if (delta < 0)
+	if (delta <= 0)
 		delta = 1;
 	p->qth_delta	= delta;
 	if (!max_P) {