RFR: 8348384: RISC-V: Disable auto-enable Vector on buggy kernels

[Robbin Ehn]

Hi please consider!

Linux kernels pre-6.9 can copy a dirty v-state during signal return path:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/arch/riscv/kernel/signal.c?h=v6.13-rc1&id=c27fa53b858b4ee6552a719aa599c250cf98a586

We should not auto-enable vector with such kernel, as we must be able to receive signals during the execution of vector code.

Manual tested pre and post 6.9 as expected.

Thanks, Robbin

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Commit messages:
 - No V <6.9

Changes: https://git.openjdk.org/jdk/pull/23256/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23256&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8348384
  Stats: 14 lines in 1 file changed: 13 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/23256.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23256/head:pull/23256

PR: https://git.openjdk.org/jdk/pull/23256