RFR: 8360405: [PPC64] some environments don't support mfdscr instruction

[Martin Doerr]

See https://github.com/openjdk/jdk/pull/20262#issuecomment-2999872960

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Commit messages:
 - 8360405: [PPC64] some environments don't support mfdscr instruction

Changes: https://git.openjdk.org/jdk/pull/25953/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25953&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8360405
  Stats: 70 lines in 4 files changed: 32 ins; 0 del; 38 mod
  Patch: https://git.openjdk.org/jdk/pull/25953.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25953/head:pull/25953

PR: https://git.openjdk.org/jdk/pull/25953