RISC-V: hwprobe: Expose Zicbom extension and its block size

Expose Zicbom through hwprobe and also provide a key to extract its
respective block size.

[ alex: Fix merge conflicts and hwprobe numbering ]

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Samuel Holland <samuel.holland@sifive.com>
Signed-off-by: Yunhui Cui <cuiyunhui@bytedance.com>
Link: https://lore.kernel.org/r/20250226063206.71216-3-cuiyunhui@bytedance.com


Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>