platform/x86/intel/vsec: Add PMT read callbacks

platform/x86/intel/vsec: Add PMT read callbacks

Some PMT providers require device specific actions before their telemetry
can be read. Provide assignable PMT read callbacks to allow providers to
perform those actions.

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: David E. Box <david.e.box@linux.intel.com>
Link: https://lore.kernel.org/r/20240725122346.4063913-3-michael.j.ruhl@intel.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>