riscv: Add new CSRs introduced by Sscofpmf[1] extension

[1] https://drive.google.com/file/d/1KcjgbLM5L1ZKY8934aJl8aQwGlMz6Cbo/view



Reviewed-by: Xiang W <wxjstz@126.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>
Signed-off-by: Atish Patra <atish.patra@wdc.com>