RFR: 8320363: ppc64 TypeEntries::type_unknown logic looks wrong, missed optimization opportunity

[Martin Doerr]

The `TypeEntries::type_unknown` logic uses a wrong register. This results in unnecessary profile updates if the type is already flagged as unknown. Doesn't cause VM errors, but may affect performance. However, I haven't seen performance impact in larger benchmarks.

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Commit messages:
 - 8320363: ppc64 TypeEntries::type_unknown logic looks wrong, missed optimization opportunity

Changes: https://git.openjdk.org/jdk/pull/16801/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16801&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8320363
  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/16801.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16801/head:pull/16801

PR: https://git.openjdk.org/jdk/pull/16801