net/mlx5: Fix error return code in esw_qos_create()

Fix to return a negative error code from the error handling
case instead of 0, as done elsewhere in this function.

Fixes: 85c5f7c9 ("net/mlx5: E-switch, Create QoS on demand")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>