fix: Fix DDO pledge math

[simlecode]

关联的Issues (Related Issues)

https://github.com/filecoin-project/lotus/pull/12341/files

改动 (Proposed Changes)

调整 DDO 订单计算质押的逻辑

附注 (Additional Info)

自查清单 (Checklist)

在你认为本 PR 满足被审阅的标准之前，需要确保 / Before you mark the PR ready for review, please make sure that:

• 符合 Venus 项目管理规范中关于 PR 的相关标准 / The PR follows the PR standards set out in the Venus project management guidelines
• 具有清晰明确的 commit message / All commits have a clear commit message.
• 包含相关的的测试用例或者不需要新增测试用例 / This PR has tests for new functionality or change in behaviour or not need to add new tests.
• 包含相关的的指南以及文档或者不需要新增文档 / This PR has updated usage guidelines and documentation or not need
• 通过必要的检查项 / All checks are green

[LinZexiao]

LGTM