ACPI: processor: Make ACPI_PROCESSOR_CSTATE depend on ACPI_PROCESSOR

To avoid build errors when CONFIG_ACPI_PROCESSOR_CSTATE is set and
CONFIG_ACPI_PROCESSOR is not (that may appear in randconfig builds),
make the former depend on the latter.

Acked-by: Len Brown <len.brown@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>