[lworld+fp16] RFR: 8339076: Float16.valueOf(long) incorrectly returns infinities in some cases

[Raffaello Giulietti]

Corrects a bug whereby Float16.valueOf(long) could erroneously return an infinity.

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Commit messages:
 - 8339076: Float16.valueOf(long) incorrectly returns infinities in some cases

Changes: https://git.openjdk.org/valhalla/pull/1225/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1225&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339076
  Stats: 15 lines in 2 files changed: 10 ins; 1 del; 4 mod
  Patch: https://git.openjdk.org/valhalla/pull/1225.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1225/head:pull/1225

PR: https://git.openjdk.org/valhalla/pull/1225