hash: fix key store element alignment

hash: fix key store element alignment

Fix the key store array element alignment such that every array
element is aligned on KEY_ALIGNMENT boundary. This is required to
make 'pdata' in 'struct rte_hash_key' align on its natural boundary
for atomic load/store.

Fixes: 473d1bebce43 ("hash: allow to store data in hash table")
Cc: stable@dpdk.org
Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Reviewed-by: Gavin Hu <gavin.hu@arm.com>
Reviewed-by: Ola Liljedahl <ola.liljedahl@arm.com>
Reviewed-by: Steve Capper <steve.capper@arm.com>
Reviewed-by: Yipeng Wang <yipeng1.wang@intel.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>