mlxsw: reg: Add Ports Module Administrative and Operational Status Register

PMAOS register configures and retrieves the per module status.
The register is used also for enabling event for status change.

It will be used to enable PMPE (Port Module Plug/Unplug) event.

Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>