RFR: 8343115: SkipIfEqual class is not used after JDK-8335946

[Fei Yang]

Hi, please review this cleanup change.
This simply removed SkipIfEqual class for all cpu platforms as it's not used anymore after JDK-8335946.

Testing:
- [x] GHA

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

Commit messages:
 - 8343115: SkipIfEqual class is not used after JDK-8335946

Changes: https://git.openjdk.org/jdk/pull/21731/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21731&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8343115
  Stats: 184 lines in 11 files changed: 0 ins; 184 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/21731.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21731/head:pull/21731

PR: https://git.openjdk.org/jdk/pull/21731