[jdk25u-dev] RFR: 8362284: RISC-V: cleanup NativeMovRegMem

[Fei Yang]

Hi all,

This pull request contains a backport of commit [3fd89be6](https://github.com/openjdk/jdk/commit/3fd89be6d1a51b6fc99f4c0b5daba7a4bd64a08e) from the [openjdk/jdk](https://git.openjdk.org/jdk) repository.

The commit being backported was authored by Hamlin Li on 17 Jul 2025 and was reviewed by Fei Yang and Ludovic Henry.

Thanks!

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Commit messages:
 - Backport 3fd89be6d1a51b6fc99f4c0b5daba7a4bd64a08e

Changes: https://git.openjdk.org/jdk25u-dev/pull/41/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk25u-dev&pr=41&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8362284
  Stats: 40 lines in 2 files changed: 0 ins; 33 del; 7 mod
  Patch: https://git.openjdk.org/jdk25u-dev/pull/41.diff
  Fetch: git fetch https://git.openjdk.org/jdk25u-dev.git pull/41/head:pull/41

PR: https://git.openjdk.org/jdk25u-dev/pull/41