RFR: 8343774: compiler/c2/TestCastX2NotProcessedIGVN.java fails on ppc64(le) & s390x platforms

[Richard Reingruber]

Vectorization of the loop in `test2` does not work on ppc therefore I want to exclude it there.

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Commit messages:
 - Exclude ppc64

Changes: https://git.openjdk.org/jdk/pull/21975/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21975&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8343774
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/21975.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21975/head:pull/21975

PR: https://git.openjdk.org/jdk/pull/21975