There is also no need to make the struct public. Also tidy up includes a
bit.

Change-Id: I188848dfd8f9ed42925b2c55da8dc4751c29f146
Reviewed-on: https://boringssl-review.googlesource.com/22126
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
Reviewed-by: Steven Valdez <svaldez@google.com>