RFR: 8327716: RISC-V: Change type of vector_length param of several assembler functions from int to uint

[Gui Cao]

Hi, we noticed that the return type of Matcher::vector_length is uint, But the type of vector_length param of several assembler functions is int, which is not consistent. This should not affect functionality, but we should change type of vector_length param of several assembler functions from int to uint to make the code clean.

### Tests
- [x] Run tier1-3 tests on on LicheePI 4A (release)
- [x]  Run tier1-3 tests with -XX:+UseRVV on qemu 8.1.0 (release)

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Commit messages:
 - Merge remote-tracking branch 'upstream/master' into JDK-8327716
 - 8327716: RISC-V: Change type of vector_length param of several assembler functions from int to uint

Changes: https://git.openjdk.org/jdk/pull/18175/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18175&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8327716
  Stats: 23 lines in 3 files changed: 0 ins; 0 del; 23 mod
  Patch: https://git.openjdk.org/jdk/pull/18175.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18175/head:pull/18175

PR: https://git.openjdk.org/jdk/pull/18175