mlxsw: reg: Extend PMMP register with new slot number field

Extend PMMP (Port Module Memory Map Properties Register) with new
field specifying the slot number. The purpose of this field is to
enable overriding the cable/module memory map advertisement.

For non-modular systems the 'module' number uniquely identifies the
transceiver location. For modular systems the transceivers are
identified by two indexes:
- 'slot_index', specifying the slot number, where line card is located;
- 'module', specifying cage transceiver within the line card.

Signed-off-by: Vadim Pasternak <vadimp@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>