mlxsw: reg: Add fields to PMAOS register

The Ports Module Administrative and Operational Status (PMAOS) register
configures and retrieves the per-module status. Extend it with fields
required to support various module settings such as reset and power
mode.

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