RFR: 8274770: [PPC64] resolve_jobject needs a generic implementation to support load barriers

[Martin Doerr]

The default implementation of BarrierSetAssembler::resolve_jobject should be generic and support all GCs. Single GCs can still implement an optimized version.

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Commit messages:
 - 8274770: [PPC64] resolve_jobject needs a generic implementation to support load barriers

Changes: https://git.openjdk.java.net/jdk/pull/5821/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5821&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8274770
  Stats: 34 lines in 3 files changed: 31 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5821.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5821/head:pull/5821

PR: https://git.openjdk.java.net/jdk/pull/5821