RFR: 8355472: Clean up x86 nativeInst after 32-bit x86 removal

[Manuel Hässig]

This PR cleans up code 32-bit x86 code in `nativeInst_x86.*` files.

Testing:
 - [x] tier1 through tier4 on x86 plus Oracle internal testing

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Commit messages:
 - Clean up 32-bit x86 code in nativeInst_x86.*

Changes: https://git.openjdk.org/jdk/pull/24911/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24911&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8355472
  Stats: 82 lines in 2 files changed: 0 ins; 81 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/24911.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24911/head:pull/24911

PR: https://git.openjdk.org/jdk/pull/24911