RFR: 8324304: RISC-V: add hw probe flags

[Hamlin Li]

Hi,
Can you help to review this simple patch to add hw probe flags?
Thanks!

Per https://github.com/torvalds/linux/blob/master/arch/riscv/include/uapi/asm/hwprobe.h, several extensions were already added in kernel code, we have several intrinsics or funtionalities depends on these extension, it's ready to add these hw probe flags already used in jdk into jdk code.

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Commit messages:
 - Initial commit

Changes: https://git.openjdk.org/jdk/pull/17519/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17519&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8324304
  Stats: 16 lines in 1 file changed: 16 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/17519.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17519/head:pull/17519

PR: https://git.openjdk.org/jdk/pull/17519