drm/xe/guc: Reformat dead CT reason string to be devcoredump compatible

The dump on a dead CT tries to emulate the devcoredump formatting (it
would use devcoredump code directly but that requires more re-work to
happen - work in progress). So update the print of the dead CT reason
code to match the format of the 'reason' string that was added to the
actual devcoredump a little while ago.

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://lore.kernel.org/r/20250325203111.3907426-1-John.C.Harrison@Intel.com