RFR: 8253029: Remove obsolete Power6 code

[David Holmes]

On Fri, 11 Sep 2020 10:22:52 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

> New pull request:
> Using a branch, updated Copyright, removed some more unused code.
> 
> [Previous text]
> The recent PPC64 platform files still contain code which is part of a Power6 optimization called Power6Scheduler.
> However, this functionality was never completely contributed so it was never usable in the OpenJDK. We should remove it
> since we're no longer optimizing for Power6.

Code changes seem fine.

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Marked as reviewed by dholmes (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/127