RFR: 8319563: Reformat code in the FFM API

[Per Minborg]

This PR proposes to reformat a small number of code line for better appearance.

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Commit messages:
 - Reformat some code

Changes: https://git.openjdk.org/jdk/pull/16529/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16529&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319563
  Stats: 12 lines in 3 files changed: 7 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/16529.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16529/head:pull/16529

PR: https://git.openjdk.org/jdk/pull/16529