[riscv-port-jdk17u:riscv-port] RFR: 8293474: RISC-V: Unify the way of moving function pointer

[Dingli Zhang]

Please review this backport to riscv-port-jdk17u.
Backport of [JDK-8293474](https://bugs.openjdk.org/browse/JDK-8293474).
The original patch cannot be directly applied because of https://github.com/openjdk/riscv-port-jdk17u/pull/32 , and there are no other additional changes.

Testing:
- Tier1-3 passed without new failure on unmacthed (release).

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Commit messages:
 - 8293474: RISC-V: Unify the way of moving function pointer

Changes: https://git.openjdk.org/riscv-port-jdk17u/pull/35/files
 Webrev: https://webrevs.openjdk.org/?repo=riscv-port-jdk17u&pr=35&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8293474
  Stats: 29 lines in 3 files changed: 2 ins; 10 del; 17 mod
  Patch: https://git.openjdk.org/riscv-port-jdk17u/pull/35.diff
  Fetch: git fetch https://git.openjdk.org/riscv-port-jdk17u.git pull/35/head:pull/35

PR: https://git.openjdk.org/riscv-port-jdk17u/pull/35