[lworld] RFR: 8338260: [lworld] assert(elements_end <= obj_end) failed: payload must fit in object

[David Simms]

Adjust flatArrayKlass oop creation for 8139457

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Commit messages:
 - 8338260: [lworld] assert(elements_end <= obj_end) failed: payload must fit in object

Changes: https://git.openjdk.org/valhalla/pull/1217/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1217&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8338260
  Stats: 8 lines in 2 files changed: 5 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/valhalla/pull/1217.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1217/head:pull/1217

PR: https://git.openjdk.org/valhalla/pull/1217