Found with -Wtype-limits. Change-Id: I5580f179425bc6b09ff2a8559fce121b0cc8ae14 Signed-off-by: Piotr Sikora <piotrsikora@google.com> Reviewed-on: https://boringssl-review.googlesource.com/6463 Reviewed-by: Adam Langley <agl@google.com>