[jdk25u] RFR: 8360179: RISC-V: Only enable BigInteger intrinsics when AvoidUnalignedAccess == false

[Fei Yang]

8360179: RISC-V: Only enable BigInteger intrinsics when AvoidUnalignedAccess == false

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Commit messages:
 - Backport 34412da52b41e9374168e67e3b6129576c8e4402

Changes: https://git.openjdk.org/jdk25u/pull/5/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk25u&pr=5&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8360179
  Stats: 132 lines in 3 files changed: 21 ins; 102 del; 9 mod
  Patch: https://git.openjdk.org/jdk25u/pull/5.diff
  Fetch: git fetch https://git.openjdk.org/jdk25u.git pull/5/head:pull/5

PR: https://git.openjdk.org/jdk25u/pull/5