RFR: 8342042: PPC64: compiler_fast_unlock_object flags failure instead of success

[Richard Reingruber]

This change inverts the `EQ` bit in `flag` with a condition register nand instruction in order to meet the post condition given at L2751-L2752:


  // flag == EQ indicates success, decrement held monitor count
  // flag == NE indicates failure


The fix passed our CI testing with LockingMode set to LM_LEGACY
Tier1-4 of hotspot and jdk. All of Langtools and jaxp. Renaissance Suite and SAP specific tests.
Testing was done on the main platforms and also on Linux/PPC64le and AIX.

The test runtime/logging/MonitorInflationTest.java failed on all platforms. Apparently it has issues with LM_LEGACY.

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Commit messages:
 - Must reach success with flag == EQ

Changes: https://git.openjdk.org/jdk/pull/21496/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21496&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8342042
  Stats: 6 lines in 1 file changed: 2 ins; 2 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/21496.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21496/head:pull/21496

PR: https://git.openjdk.org/jdk/pull/21496