RFR: 8307907: [ppc] Remove RTM locking implementation [v3]

[Martin Doerr]

On Wed, 14 Jun 2023 14:31:41 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

>> This PR removes RTM code for PPC64. The instructions are not supported by Power10 processors.
>> The situation is even worse in Power9 compatibility mode on Power10. The VM detects RTM to be available, but the processor is unable to complete any transaction successfully.
>> The feature had so many problems and we never supported it in production.
>
> Martin Doerr has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Remove more leftovers from RTM.

Thanks for the review!

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PR Comment: https://git.openjdk.org/jdk/pull/14398#issuecomment-1591377041