ec-nist: use global vone and vzero
* mpi/ec-nist.c (vzero, vone): Remove. (_gcry_mpi_ec_nist192_mod, _gcry_mpi_ec_nist224_mod) (_gcry_mpi_ec_nist256_mod, _gcry_mpi_ec_nist384_mod): Use _gcry_ct_vzero and _gcry_ct_vone.
Cherry pick master commit of:
5c5ba1ec2b505726ee1311339ac9e8b5c62cac4a
- Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>