net/mlx5: fix build without soft counters
net/mlx5: fix build without soft counters

total_length is only visible when SOFT_COUNTERS are enabled

Fixes: 3f13f8c23a7c ("net/mlx5: support hardware TSO")
Cc: stable@dpdk.org

Signed-off-by: Thierry Herbelot <6a957105cd34caef8a0a517243bc5f366ed82fb3@6wind.com>
Acked-by: Nelio Laranjeiro <2f8dd9032d5b85ca4b53dec8ce664eb6998836be@6wind.com>

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