[llvm] [RISCV] Check hasVInstructions() rather than hasStdExtZbb() for UMAX/UMIN/SMAX/SMIN combines. (PR #189506)

[via llvm-commits]

dyung wrote:

> LLVM Buildbot has detected a new failure on builder `llvm-clang-x86_64-sie-ubuntu-fast` running on `sie-linux-worker` while building `llvm` at step 6 "test-build-unified-tree-check-all".
> 
> Full details are available at: https://lab.llvm.org/buildbot/#/builders/144/builds/50491
> 
> Here is the relevant piece of the build log for the reference

Please ignore this failure, I had left some changes on the bot that I forgot to clean up while testing something out. Sorry about the noise.

https://github.com/llvm/llvm-project/pull/189506