net/mlx5: Unlock on error in mlx5_sriov_enable()

Unlock before returning if mlx5_device_enable_sriov() fails.

Fixes: 84a433a4 ("net/mlx5: Lock mlx5 devlink reload callbacks")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>