net/mlx5: Move all internal timer metadata into a dedicated struct

Internal timer mode (SW clock) requires some PTP clock related metadata
structs. Real time mode (HW clock) will not need these metadata structs.
This separation emphasize the different interfaces for HW clock and SW
clock.

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