mlxsw: spectrum: PTP: Support SIOCGHWTSTAMP, SIOCSHWTSTAMP ioctls

The SIOCSHWTSTAMP ioctl configures HW timestamping on a given port.
Dispatch the ioctls to per-chip handler (which add to ptp_ops). Find
which PTP messages need to be timestamped and configure MTPPPC
accordingly.

The SIOCGHWTSTAMP ioctl is getter for the current configuration.

Signed-off-by: Petr Machata <petrm@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>