RFR: 8330049: Remove unused AbstractLinker::linkerByteOrder

[Jorn Vernee]

Please review this simple cleanup which removes the `AbstractLinker::linkerByteOrder` method. It was only used in `AixPPC64Linker`, where we know it will always return `ByteOrder.BIG_ENDIAN` so we can just replace the call with that.

Testing: Local run of `run-test-jdk_foreign`.

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Commit messages:
 - Remove unused AbstractLinker::linkerByteOrder

Changes: https://git.openjdk.org/jdk/pull/18726/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18726&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8330049
  Stats: 59 lines in 12 files changed: 0 ins; 58 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/18726.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18726/head:pull/18726

PR: https://git.openjdk.org/jdk/pull/18726