RFR: 8356875: RISC-V: extension flag UseZvfh should depends on UseZfh

[Hamlin Li]

Hi,
Can you help to review this simple patch?
If we don't enable such dependency, then there will be situation that when Zvfh is enabled but Zfh is disabled, and optimizations depending on Zvfh will be disabled (e.g. in C2) because Zfh related IR node are considered not supported.

Thanks!

By [rvv spec](https://github.com/riscvarchive/riscv-v-spec/blob/master/v-spec.adoc#185-zvfh-vector-extension-for-half-precision-floating-point), `The Zvfh extension depends on the Zve32f and Zfhmin extensions.`
But I think in logic and JVM code, we should let `Zvfh` depends on `Zfh`.

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Commit messages:
 - initial commit

Changes: https://git.openjdk.org/jdk/pull/25213/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25213&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8356875
  Stats: 9 lines in 1 file changed: 6 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/25213.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25213/head:pull/25213

PR: https://git.openjdk.org/jdk/pull/25213