platform/x86: mlx-platform: Set system mux configuration based on system type

Separate assignment for systems mux configuration based on system type,
instead of setting the same configuration for the all.
The motivation is to allow introduction of new systems types with the
different mux topology.

Signed-off-by: Vadim Pasternak <vadimp@mellanox.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>