target/riscv: Add support for Zfbfmin extension

target/riscv: Add support for Zfbfmin extension

Add trans_* and helper function for Zfbfmin instructions.

Signed-off-by: Weiwei Li <liweiwei@iscas.ac.cn>
Signed-off-by: Junqiang Wang <wangjunqiang@iscas.ac.cn>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230615063302.102409-3-liweiwei@iscas.ac.cn>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>