ACPI: processor: idle: Optimize ACPI idle driver registration

ACPI: processor: idle: Optimize ACPI idle driver registration

Currently, the ACPI idle driver is registered from within a CPU
hotplug callback. Although this didn't cause any functional issues,
this is questionable and confusing. And it is better to register
the cpuidle driver when all of the CPUs have been brought up.

So add a new function to initialize acpi_idle_driver based on the
power management information of an available CPU and register cpuidle
driver in acpi_processor_driver_init().

This commit has four changes under the commit 7a8c994cbb2d (ACPI:
processor: idle: Optimize ACPI idle driver registration):

 1) move acpi_processor_register_idle_driver() ahead of the
    driver_register().
 2) add acpi_processor_cstate_first_run_checks() before calling
    acpi_processor_get_power_info().
 3) squash the commit 9d68320b2bca (ACPI: processor: idle: Fix
    function defined but not used warning) into this change.
 4) use for_each_possible_cpu(cpu) to scan all possible cpus.

Signed-off-by: Huisong Li <lihuisong@huawei.com>
Tested-by: Borislav Petkov (AMD) <bp@alien8.de>
[ rjw: New comment edits, changelog tweak ]
Link: https://patch.msgid.link/20251223100914.2407069-2-lihuisong@huawei.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>