RFR: 8338124: C2 SuperWord: MulAddS2I input permutation still partially broken after JDK-8333840

[Emanuel Peter]

[JDK-8333840](https://bugs.openjdk.org/browse/JDK-8333840) attempted to fix some input permutation cases. Sadly, there is a typo which means that there can still be some broken cases that produce wrong results.

`MulAddS2I` is a special case, where we have to verify that the 4 inputs for all members of the pack are in the same permutation. I only started the checking on the second element. This worked on all my previous examples, but does not work on the added regression test. We must, of course, start the checking on the first element.

-------------

Commit messages:
 - JDK-8338124

Changes: https://git.openjdk.org/jdk/pull/20539/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20539&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8338124
  Stats: 18 lines in 2 files changed: 16 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/20539.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20539/head:pull/20539

PR: https://git.openjdk.org/jdk/pull/20539