RFR: 8307104: [AIX] VM crashes with UseRTMLocking on Power10

[Martin Doerr]

We need to prevent usage of transactional memory (UseRTMLocking) on Power10 which doesn't support it. The VM crashes with SIGILL on AIX when trying to use it.

I'm also changing the AIX specific check for the case in which somebody uses Power10 with -XX:PowerArchitecturePPC64=8 (or 9).
The Linux specific code is fine as it is.

This change is small and should get considered for backports. We may remove the RTM code completely for future JDKs.

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Commit messages:
 - 8307104: [AIX] VM crashes with UseRTMLocking on Power10

Changes: https://git.openjdk.org/jdk/pull/13717/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13717&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8307104
  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/13717.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13717/head:pull/13717

PR: https://git.openjdk.org/jdk/pull/13717