mlxsw: reg: Add Monitoring Global Configuration Register

This register serves to configure global parameters of certain
monitoring operations. The following patches will use it to configure
that when PTP timestamps are delivered through the PTP FIFO traps, the
FIFO in question is cleared as well.

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>