platform/x86: mlx-platform: Fix extended topology configuration for power supply units

Fix topology configuration for power supply units in structure
'mlxplat_mlxcpld_ext_pwr_items_data', due to hardware change.

Note: no need to backport the fix, since there is no such hardware yet
(equipped with four power) at the filed.

Signed-off-by: Vadim Pasternak <vadimp@nvidia.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>