platform/x86/intel/vsec: Add private data for per-device data

platform/x86/intel/vsec: Add private data for per-device data

Introduce a new private structure, struct vsec_priv, to hold a pointer to
the platform-specific information. Although the driver didn’t previously
require this per-device data, adding it now lays the groundwork for
upcoming patches that will manage such data. No functional changes.

Signed-off-by: David E. Box <david.e.box@linux.intel.com>
Link: https://lore.kernel.org/r/20250703022832.1302928-3-david.e.box@linux.intel.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>