ACPI: CPPC: Add IS_OPTIONAL_CPC_REG macro to judge if a cpc_reg is optional

ACPI: CPPC: Add IS_OPTIONAL_CPC_REG macro to judge if a cpc_reg is optional

In ACPI 6.5, s8.4.6.1 _CPC (Continuous Performance Control), whether
each of the per-cpu cpc_regs[] is mandatory or optional is defined.

Since the CPC_SUPPORTED() check is only for optional _CPC fields,
another macro to check if the field is optional is needed.

Reviewed-by: Pierre Gondois <pierre.gondois@arm.com>
Signed-off-by: Lifeng Zheng <zhenglifeng1@huawei.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Link: https://patch.msgid.link/20250411093855.982491-2-zhenglifeng1@huawei.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>