scd: Fix keytocard for ECC.
* scd/app-openpgp.c (build_ecc_privkey_template): Size can be greater than 128 when it comes with public key for curve of larger field.
- Reported-by: Arnaud Fontaine <arnaud.fontaine@ssi.gouv.fr>
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>