fcrypt_preparekey
void fcrypt_preparekey(struct fcrypt_key *key, const u8 raw_key[FCRYPT_BSIZE]);
EXPORT_SYMBOL_IF_KUNIT(fcrypt_preparekey);
fcrypt_preparekey(ci, token->kad->session_key);
fcrypt_preparekey(&cipher, session_key->x);
fcrypt_preparekey(&key, tv->key);