pk: Add infrastructure for non-fatal cache validation errors
pk: Add infrastructure for non-fatal cache validation errors

- Allow cache validate functions to set the damaged flag independent
of their return code, because we may need to allow checks to continue
even though the cache is damaged

- Restructure validate_cache() exit path

cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr