RFR: 8369257: PPC: compiler/whitebox/RelocateNMethodMultiplePaths.java fails with assertion

[Richard Reingruber]

Relax assertion in NativePostCallNop::patch(). With NMethodRelocation (see [JDK-8369257](https://bugs.openjdk.org/browse/JDK-8369257)) it cannot be expected that the post call nop to be patched is still clean.

compiler/whitebox/RelocateNMethodMultiplePaths.java succeeds in local testing on PPC.

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Commit messages:
 - Expect already patched NativePostCallNop with NMethodRelocation

Changes: https://git.openjdk.org/jdk/pull/27669/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27669&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8369257
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/27669.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27669/head:pull/27669

PR: https://git.openjdk.org/jdk/pull/27669