net/mlx5e: Cleanup PTP

Reduce scope of mlx5e_ptp_params, move to its c file. Remove unneeded
variables from mlx5e_ptp_open and state bitmap from PTP channel. In
addition, remove channel index from PTP channel since it is set to a
hard coded value, use define instead.

Signed-off-by: Aya Levin <ayal@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>