[clang] [RISCV] Split out the intrinsic tests for bfloat16 into a separate directory named zvfbfmin. NFC. (PR #147644)

[Jim Lin via cfe-commits]

tclin914 wrote:

> I agree with you that it's easier to maintain, btw are you going to do that for all extensions?

For now, I'm going to do this for zvfh/zvfhmin/zvfbfmin/zvfbfwma.

https://github.com/llvm/llvm-project/pull/147644