RFR: 8339411: [PPC64] cmpxchgw/h/b doesn't handle external Label

[Martin Doerr]

I had forgotten to copy one line from the cmpxchgd in [JDK-8338814](https://bugs.openjdk.org/browse/JDK-8338814) (https://github.com/openjdk/jdk/commit/2edf574f62837678e621e1dfdd8d8a77dbe17ad6).

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Commit messages:
 - 8339411: [PPC64] cmpxchgw/h/b doesn't handle external Label

Changes: https://git.openjdk.org/jdk/pull/20826/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20826&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339411
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/20826.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20826/head:pull/20826

PR: https://git.openjdk.org/jdk/pull/20826