RFR: 8316743: RISC-V: Change UseVectorizedMismatchIntrinsic option result to warning

[Ilya Gavrilin]

Please review this small change for UseVectorizedMismatchIntrinsic option.
On RISC-V we do not have VectorizedMismatch intrinsic, so `void LIRGenerator::do_vectorizedMismatch(Intrinsic* x)` prodeuces fatal error when this option turned on.
Other similar options (like -XX:+UseCRC32Intrinsics) produces only warning: https://github.com/openjdk/jdk/blob/c90d63105ca774c047d5f5a4348aa657efc57953/src/hotspot/cpu/riscv/vm_version_riscv.cpp#L150-L183
Also, on platforms, where VectorizedMismatch unimplemented to we got warning.

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Commit messages:
 - UseVectroizedMismatchIntrinsic option update RISC-V

Changes: https://git.openjdk.org/jdk/pull/15890/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15890&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316743
  Stats: 6 lines in 2 files changed: 5 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/15890.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15890/head:pull/15890

PR: https://git.openjdk.org/jdk/pull/15890