RFR: 8356556: AArch64: No need for acquire fence in safepoint poll in FFM

[Samuel Chee]

Removes the unnecessary acquire to reduce memory ordering requirement since it is not longer needed as threads always disarm their own poll value.

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Commit messages:
 - 8356556: AArch64: No need for acquire fence in safepoint poll in FFM

Changes: https://git.openjdk.org/jdk/pull/25211/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25211&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8356556
  Stats: 19 lines in 8 files changed: 0 ins; 7 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/25211.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25211/head:pull/25211

PR: https://git.openjdk.org/jdk/pull/25211