app/flow-perf: use macro for cache alignment

The macro __rte_cache_aligned is better suited for aligning
a structure on a cache line (of any size).

Fixes: 15c4318640 ("app/flow-perf: add packet forwarding support")

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Wisam Jaddo <wisamm@mellanox.com>

app/test-flow-perf/main.c

@@ -84,7 +84,7 @@ struct lcore_info {
 	uint64_t tx_drops;
 	uint64_t rx_pkts;
 	struct rte_mbuf *pkts[MAX_PKT_BURST];
-} __attribute__((__aligned__(64))); /* let it be cacheline aligned */
+} __rte_cache_aligned;
 
 static struct lcore_info lcore_infos[MAX_LCORES];