net/mlx5: DR, Fix error return code in dr_domain_init_resources()

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

Fixes: 4ec9e7b0

 ("net/mlx5: DR, Expose steering domain functionality")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>