gpg: Clean up ECDH code path (4).
* g10/ecdh.c (prepare_ecdh_with_shared_point): New. (pk_ecdh_encrypt_with_shared_point): Fixing error paths for closing the cipher handle, use prepare_ecdh_with_shared_point.
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>