RFR: 8370244: [PPC64] Several vector tests fail on Power8

[Martin Doerr]

This is a workaround for [JDK-8370803](https://bugs.openjdk.org/browse/JDK-8370803). Power8 uses `MaxVectorSize`=8 by default. All tests are passing with `EnableVectorSupport` disabled.

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Commit messages:
 - 8370244: [PPC64] Several vector tests fail on Power8

Changes: https://git.openjdk.org/jdk/pull/28214/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28214&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8370244
  Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/28214.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28214/head:pull/28214

PR: https://git.openjdk.org/jdk/pull/28214