RISC-V: cacheflush: Initialize CBO variables on ACPI systems

Initialize the CBO variables on ACPI based systems using information in
RHCT.

Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Samuel Holland <samuel.holland@sifive.com>
Link: https://lore.kernel.org/r/20231018124007.1306159-5-sunilvl@ventanamicro.com


Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>