net/mlx5: Change parameters for PTP internal functions

In later patch, the mlx5_clock will be allocated dynamically, its
address can be obtained from mlx5_core_dev struct, but mdev can't be
obtained from mlx5_clock because it can be shared by multiple
interfaces. So change the parameter for such internal functions, only
mdev is passed down from the callers.

Signed-off-by: Jianbo Liu <jianbol@nvidia.com>
Reviewed-by: Carolina Jubran <cjubran@nvidia.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>