net/mlx5e: CT: remove set but not used variable 'unnew'

drivers/net/ethernet/mellanox/mlx5/core/en/tc_ct.c:
 In function mlx5_tc_ct_parse_match:
drivers/net/ethernet/mellanox/mlx5/core/en/tc_ct.c:699:36: warning:
 variable unnew set but not used [-Wunused-but-set-variable]

Fixes: 4c3844d9

 ("net/mlx5e: CT: Introduce connection tracking")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>