scd:openpgp: Add the length check for new PIN.
* scd/app-openpgp.c (do_change_pin): Make sure new PIN length is longer than MINLEN.
(cherry picked from commit 2376cdff1318688d94c95fd01adc4b2139c4a8c7)
- GnuPG-bug-id: T6843
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>