ecc: Avoid double conversion to affine coordinates in keygen.
* cipher/ecc.c (nist_generate_key): Add args r_x and r_y. (ecc_generate): Rename vars. Convert to affine coordinates only if not returned by the lower level generation function.
nist_generate_key already needs to convert to affine coordinates to
implement Jivsov's trick. Thus we can return them and avoid calling
it in ecc_generate again.
- Signed-off-by: Werner Koch <wk@gnupg.org>