mlxsw: reg: Add the Monitoring Port Analyzer register

The MPAR register is used to bind ports to a SPAN entry (which was
created using MPAT register) and thus mirror their traffic (ingress /
egress) to a different port.

Signed-off-by: Yotam Gigi <yotamg@mellanox.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>