[jdk17u-dev] RFR: 8304880: [PPC64] VerifyOops code in C1 doesn't work with ZGC

[Martin Doerr]

Backport of [JDK-8304880](https://bugs.openjdk.org/browse/JDK-8304880). Doesn't apply cleanly, but this change is trivial to backport because it only removes 2 small code pieces. (Can't verify oops between raw load and load barrier with ZGC.)

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

Commit messages:
 - Backport 695683b5b15c69a56fe7ee1a93482fe7c3530ca8

Changes: https://git.openjdk.org/jdk17u-dev/pull/1225/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1225&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8304880
  Stats: 2 lines in 1 file changed: 0 ins; 2 del; 0 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/1225.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/1225/head:pull/1225

PR: https://git.openjdk.org/jdk17u-dev/pull/1225