RFR: 8323660: Serial: Fix header ordering and indentation

[Lei Zaakjyu]

follow up 8234502.

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Commit messages:
 - fix header ordering

Changes: https://git.openjdk.org/jdk/pull/17398/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17398&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8323660
  Stats: 33 lines in 4 files changed: 15 ins; 18 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/17398.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17398/head:pull/17398

PR: https://git.openjdk.org/jdk/pull/17398