RFR: 8301818: RISC-V: Small Optimizing for use mv to replace mvw

[Gui Cao]

HI,

The two functions of mvw and mv overlap, we can use mv to replace mvw, so the mvw function can be removed. and format some code.
## Testing:
- all tier1 on unmatched board without new failures

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Commit messages:
 - Small Optimizing for use mv to replace mvw

Changes: https://git.openjdk.org/jdk/pull/12425/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12425&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8301818
  Stats: 31 lines in 9 files changed: 0 ins; 2 del; 29 mod
  Patch: https://git.openjdk.org/jdk/pull/12425.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12425/head:pull/12425

PR: https://git.openjdk.org/jdk/pull/12425