ACPI: Enable ACPI_PROCESSOR for RISC-V

The ACPI processor driver is not currently enabled for RISC-V.
This is required to enable CPU related functionalities like
LPI and CPPC. Hence, enable ACPI_PROCESSOR for RISC-V.

Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20240118062930.245937-4-sunilvl@ventanamicro.com


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