RFR: 8357626: RISCV: Tighten up template interpreter method entry code

[Anjian Wen]

do the same thing as x86/AArch64 but for RISCV
[JDK-8352415](https://bugs.openjdk.org/browse/JDK-8352415) 
[JDK-8356949](https://bugs.openjdk.org/browse/JDK-8356949)

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Commit messages:
 - change reg use
 - RISCV: Tighten up template interpreter method entry code

Changes: https://git.openjdk.org/jdk/pull/25412/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25412&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8357626
  Stats: 19 lines in 1 file changed: 10 ins; 2 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/25412.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25412/head:pull/25412

PR: https://git.openjdk.org/jdk/pull/25412