platform/x86/intel/vsec: allocate res with intel_vsec_dev

platform/x86/intel/vsec: allocate res with intel_vsec_dev

Use a flexible array member to combine allocations. Avoids having to
free separately.

Add __counted_by for extra runtime analysis.

Move counting variable assignment to after allocations as is already
done by kzalloc_flex for GCC 15 and above.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
Tested-by: David E. Box <david.e.box@linux.intel.com>
Reviewed-by: David E. Box <david.e.box@linux.intel.com>
Link: https://patch.msgid.link/20260430224307.109311-1-rosenp@gmail.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>