scd:nks: Get the PIN prompts right for the Signature Card
* scd/app-nks.c (get_dispserialno): Move more to the top. (do_getattr): Add $DISPSERIALNO and SERIALNO. Make CHV-STATUS work with NKS15. (verify_pin): Use dedicated min. PIN lengths. (parse_pwidstr): Support NKS15
- GnuPG-bug-id: T4938
- Signed-off-by: Werner Koch <wk@gnupg.org>