[riscv-port-jdk17u:riscv-port] RFR: 8293100: RISC-V: Need to save and restore callee-saved FloatRegisters in StubGenerator::generate_call_stub

[Gui Cao]

Please review this backport to riscv-port-jdk17u. Backport of [JDK-8293100](https://bugs.openjdk.org/browse/JDK-8293100).
The original patch cannot be directly applied because of the line number, but there are no other additional changes.

Testing:

- vmTestbase/nsk/stress/jni/jnistress002.java passed on qemu and unmacthed.
- all tier1 passed on unmacthed (release).

-------------

Commit messages:
 - backport JDK-8293100

Changes: https://git.openjdk.org/riscv-port-jdk17u/pull/4/files
 Webrev: https://webrevs.openjdk.org/?repo=riscv-port-jdk17u&pr=4&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8293100
  Stats: 81 lines in 4 files changed: 64 ins; 0 del; 17 mod
  Patch: https://git.openjdk.org/riscv-port-jdk17u/pull/4.diff
  Fetch: git fetch https://git.openjdk.org/riscv-port-jdk17u pull/4/head:pull/4

PR: https://git.openjdk.org/riscv-port-jdk17u/pull/4