RFR: 8365146: Remove LockingMode related code from ppc64 [v3]

[Fredrik Bredberg]

> 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 **ppc64** 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 with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:

 - Merge branch 'master' into 8365146_remove_lockingmode_ppc64
 - Update after review
 - Merge branch 'master' into 8365146_remove_lockingmode_ppc64
 - 8365146: Remove LockingMode related code from ppc64

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/26697/files
  - new: https://git.openjdk.org/jdk/pull/26697/files/e9c74f13..c396dcae

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26697&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26697&range=01-02

  Stats: 10407 lines in 339 files changed: 6619 ins; 2633 del; 1155 mod
  Patch: https://git.openjdk.org/jdk/pull/26697.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26697/head:pull/26697

PR: https://git.openjdk.org/jdk/pull/26697