net: mscc: ocelot: use list_add_tail in ocelot_vcap_filter_add_to_block()

list_add(..., pos->prev) and list_add_tail(..., pos) are equivalent, use
the later form to unify with the case where the list is empty later.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/mscc/ocelot_vcap.c

@@ -1013,7 +1013,7 @@ static int ocelot_vcap_filter_add_to_block(struct ocelot *ocelot,
 		if (filter->prio < tmp->prio)
 			break;
 	}
-	list_add(&filter->list, pos->prev);
+	list_add_tail(&filter->list, pos);
 
 	return 0;
 }