Integrate ppc64 fixes

[TheRealMDoerr]

2 PPC64 fixes from jdk master. There were only 2 simple hunks to resolve (in ZSaveLiveRegisters).

---

Progress

• [ ] Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• [x] Change must not contain extraneous whitespace
• [ ] Commit message must refer to an issue

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/zgc pull/3/head:pull/3
$ git checkout pull/3

Update a local copy of the PR:
$ git checkout pull/3
$ git pull https://git.openjdk.org/zgc pull/3/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 3

View PR using the GUI difftool:
$ git pr show -t 3

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/zgc/pull/3.diff

[bridgekeeper[bot]]

:wave: Welcome back mdoerr! A progress list of the required criteria for merging this PR into zgc_generational will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[TheRealMDoerr]

Already integrated.