net/mlx5: Fix passing zero to 'PTR_ERR'

Fix smatch warnings:

drivers/net/ethernet/mellanox/mlx5/core/esw/acl/egress_lgcy.c:105 esw_acl_egress_lgcy_setup() warn: passing zero to 'PTR_ERR'
drivers/net/ethernet/mellanox/mlx5/core/esw/acl/egress_ofld.c:177 esw_acl_egress_ofld_setup() warn: passing zero to 'PTR_ERR'
drivers/net/ethernet/mellanox/mlx5/core/esw/acl/ingress_lgcy.c:184 esw_acl_ingress_lgcy_setup() warn: passing zero to 'PTR_ERR'
drivers/net/ethernet/mellanox/mlx5/core/esw/acl/ingress_ofld.c:262 esw_acl_ingress_ofld_setup() warn: passing zero to 'PTR_ERR'

esw_acl_table_create() never returns NULL, so
NULL test should be removed.

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>