platform/x86/intel/pmt: Add pre/post decode hooks around header parsing

platform/x86/intel/pmt: Add pre/post decode hooks around header parsing

Add optional pre- and post-decode callbacks to the PMT class so namespaces
can perform setup and cleanup steps around header parsing.

  - Add pmt_pre_decode() and pmt_post_decode() to struct
    intel_pmt_namespace.
  - Update intel_pmt_dev_create() to invoke, in order:
      pre → header_decode() → post.
  - Keep the existing pmt_header_decode() callback unchanged.

No functional changes. This adds flexibility for upcoming decoders while
preserving current behavior.

Signed-off-by: David E. Box <david.e.box@linux.intel.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://patch.msgid.link/b178a341601ca694db99c3b738fe4ed9e0c2bede.1781294741.git.david.e.box@linux.intel.com
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>