scd: Implement direct access by KEYGRIP for GETATTR and READKEY.
* scd/app-openpgp.c (do_readkey): Handle KEYGRIP access. * scd/command.c (do_readkey): New. (cmd_readkey): Use do_readkey supporting KEYGRIP access. (cmd_getattr): Supporting KEYGRIP access.
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>