RFR: 8368724: RISC-V: Check if unaligned_access is enabled before use

[Fei Yang]

On Fri, 26 Sep 2025 03:36:50 GMT, Anjian Wen <wenanjian at openjdk.org> wrote:

> we can notice that the `unaligned_access.value()` can only be used when the `unaligned_access.enabled()` is true, so we add the check here before use
> 
> Manually checked the result on platforms w/wo fast misaligned accesses by running: $java -XX:+PrintFlagsFinal -version | grep AvoidUnalignedAccess

Looks reasonable. Thanks.

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Marked as reviewed by fyang (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/27510#pullrequestreview-3270088455