RFR: 8281061: [s390] JFR runs into assertions while validating interpreter frames

[Martin Doerr]

s390 implementation requires small changes to avoid running into assertions in debug builds. See JBS for details.

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Commit messages:
 - 8281061: [s390] JFR runs into assertions while validating interpreter frames

Changes: https://git.openjdk.java.net/jdk/pull/7312/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7312&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8281061
  Stats: 12 lines in 2 files changed: 2 ins; 3 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7312.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7312/head:pull/7312

PR: https://git.openjdk.java.net/jdk/pull/7312