cipher:ecc: Fix public key computation for EdDSA.
* cipher/ecc-misc.c (_gcry_ecc_compute_public): Fix hard-coded length for digest lower bits.
Cherry-pick from master commit of:
469919751d6eb46ceff9df80676416ca8f474459
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>