RFR: 8349428: RISC-V: "bad alignment" with -XX:-AvoidUnalignedAccesses after JDK-8347489

[Gui Cao]

Hi, please review this small change fixing an assertion error.
As the alignment of the loading addresses is only ensured under -XX:-AvoidUnalignedAccesses, we should only enable the related assersions about the alignment under this option.


### Testing
- [x] Sanity tested with -XX:-AvoidUnalignedAccesses using fastdebug build.
- [ ] Run tier1 tests on SOPHON SG2042 (fastdebug)
- [ ] Run tier1-3 tests on Milk-V Megrez (release)

-------------

Commit messages:
 - 8349428: RISC-V: "bad alignment" with -XX:-AvoidUnalignedAccesses after JDK-8347489

Changes: https://git.openjdk.org/jdk/pull/23459/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23459&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8349428
  Stats: 35 lines in 2 files changed: 14 ins; 0 del; 21 mod
  Patch: https://git.openjdk.org/jdk/pull/23459.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23459/head:pull/23459

PR: https://git.openjdk.org/jdk/pull/23459