RFR: 8329545: [s390x] Fix garbage value being passed in Argument Register

[Sidraya Jayagond]

Fix sign extension on 4 byte load from argument stack slot to GPR.

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Commit messages:
 - Fix signed extension load from argument stack slot to GPR.

Changes: https://git.openjdk.org/jdk/pull/18601/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18601&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8329545
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/18601.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18601/head:pull/18601

PR: https://git.openjdk.org/jdk/pull/18601