platform/x86/intel/pmt: Add INTEL_PMT module namespace

Since the currently exported symbols in pmt_class are only used by other
Intel PMT drivers, create an INTEL_PMT module namespace for them.

Signed-off-by: David E. Box <david.e.box@linux.intel.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20230316225736.2856521-1-david.e.box@linux.intel.com
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>