net/mlx5: Refactor init clock function

Function mlx5_init_clock() is responsible for internal PTP related metadata
initializations. Break mlx5_init_clock() to sub functions, each takes care
of its own logic.

Signed-off-by: Eran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: Aya Levin <ayal@nvidia.com>
Reviewed-by: Moshe Shemesh <moshe@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>