Clean up the modp_b64 api

This will make any further modifications to modp_b64 easier, since we
don't have to support unused configurations or APIs.

Bug: 1383507
Change-Id: I07d42a99f0bef4988101ad99724e23101aec6baf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4023975
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Commit-Queue: Charlie Harrison <csharrison@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1071997}
NOKEYCHECK=True
GitOrigin-RevId: 51305b3e52a6cad52dfa95c29a2bbea869cb81c5
3 files changed