mlxsw: reg: Add session_id and pid to MPAT register

Allow setting session_id and pid as part of port analyzer
configurations.

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