mlxsw: core_env: Pass slot index during PMAOS register write call

Pass the slot index down to PMAOS pack helper alongside with the module.

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