RFR: 8364406: Remove LockingMode related code from aarch64

[Andrew Haley]

On Fri, 1 Aug 2025 11:22:50 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 **aarch64** 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.
> 
> Passes tier1-tier5 with no added problems.

Looks good to me.

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PR Review: https://git.openjdk.org/jdk/pull/26594#pullrequestreview-3079125218