[RISCV] Introduce and use BF16 in Xsfvfwmaccqqq intrinsics (#71140)

BF16 implementation based on @joshua-arch1's
https://reviews.llvm.org/D152498
Fixed the incorrect f16 type introduced in
https://github.com/llvm/llvm-project/pull/68296



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Co-authored-by: Jun Sha (Joshua) <cooper.joshua@linux.alibaba.com>