platform/x86/intel/pmt/crashlog: Split init into pre-decode

platform/x86/intel/pmt/crashlog: Split init into pre-decode

Refactor crashlog initialization to use the PMT namespace pre-decode hook:

  - Add pmt_crashlog_pre_decode() to parse type/version, select the
    crashlog_info, initialize the control mutex, and set entry->attr_grp.
  - Simplify pmt_crashlog_header_decode() to only read header fields from
    the discovery table.
  - Wire the namespace with .pmt_pre_decode = pmt_crashlog_pre_decode.

This separates structural initialization from header parsing, aligning
crashlog with the PMT class pre/post decode flow.

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/ed8cda8456c97132cf2d2b4ff6a5cffb1ce3a666.1781294741.git.david.e.box@linux.intel.com
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>