mlxsw: reg: Add Monitoring Time Precision Packet Port Configuration Register

This register serves for configuration of which PTP messages should be
timestamped. This is a global configuration, despite the register name.

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>