RFR: 8364570: Remove LockingMode related code from riscv64 [v2]

[Feilong Jiang]

On Fri, 8 Aug 2025 09:56:45 GMT, Fredrik Bredberg <fbredberg at openjdk.org> wrote:

>> Since the integration of [JDK-8359437](https://bugs.openjdk.org/browse/JDK-8359437) the `LockingMode` flag can no longer be set by the user, instead it's declared as `const int LockingMode = LM_LIGHTWEIGHT;`. This means that we can now safely remove all `LockingMode` related code from all platforms.
>> 
>> This PR removes `LockingMode` related code from the **riscv64** platform.
>> 
>> When all the `LockingMode` code has been removed from all platforms, we can go on and remove it from shared (non-platform specific) files as well. And finally remove the `LockingMode` variable itself.
>
> Fredrik Bredberg has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update one after review

Marked as reviewed by fjiang (Committer).

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PR Review: https://git.openjdk.org/jdk/pull/26658#pullrequestreview-3102922414