RFR: 8353219: RISC-V: Fix client builds after JDK-8345298

[Fei Yang]

Hi, please review this trivial change fixing a client build issue.
The definitions of both `generate_float16ToFloat()` and `generate_floatToFloat16()` should be moved out of `COMPILER2_OR_JVMCI` macro scope. Testing: client builds fine on linux-riscv64 with this change.

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Commit messages:
 - 8353219: RISC-V: Fix client builds after JDK-8345298

Changes: https://git.openjdk.org/jdk/pull/24307/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24307&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8353219
  Stats: 4 lines in 1 file changed: 2 ins; 2 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/24307.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24307/head:pull/24307

PR: https://git.openjdk.org/jdk/pull/24307