mlxsw: Track per-module port status

In the common port module core, track the number of logical ports that
are mapped to the port module and the number of logical ports using it
that are administratively up.

This will be used by later patches to potentially veto and control
certain operations on the module, such as reset and setting its power
mode.

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