app/flow-perf: use macro for cache alignment
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: 15c431864000 ("app/flow-perf: add packet forwarding support")

Signed-off-by: Thomas Monjalon <5f50a84c1fa3bcff146405017f36aec1a10a9e38@monjalon.net>
Acked-by: Wisam Jaddo <cbdf453c8bf861f460ccde953a2ad4b2bcf4ed16@mellanox.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk