[lworld] Integrated: 8325560: [lworld] Aarch64 interpreter is missing a membar on flat array access

[Frederic Parain]

Add missing membar in the aarch64 interpreter when reading a value from a flat array.

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Commit messages:
 - Adding missing membar on flat array reads

Changes: https://git.openjdk.org/valhalla/pull/1004/files
 Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1004&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8325560
  Stats: 3 lines in 1 file changed: 3 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/valhalla/pull/1004.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1004/head:pull/1004

PR: https://git.openjdk.org/valhalla/pull/1004