mpih-const-time: use global vzero/vone variable
* mpi/mpih-const-time.c (vzero, vone): Remove. (_gcry_mpih_set_cond, _gcry_mpih_add_n_cond, _gcry_mpih_sub_n_cond) (_gcry_mpih_swap_cond, _gcry_mpih_abs_cond): Use _gcry_ct_vzero and _gcry_ct_vone.
- Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>