EC_GROUP_cmp should return zero if the groups match.

(I got this wrong when reading the OpenSSL code.)

Change-Id: Ib289ef41d0ab5a3157ad8b9454d2de96d1f86c22
Reviewed-on: https://boringssl-review.googlesource.com/3620
Reviewed-by: Adam Langley <agl@google.com>
3 files changed