ACPI: processor: Replace deprecated CPU-hotplug functions

The functions cpu_hotplug_begin, cpu_hotplug_done, get_online_cpus() and
put_online_cpus() have been deprecated during the CPU hotplug rework. They map
directly to cpus_write_lock(), cpus_write_unlock, cpus_read_lock() and
cpus_read_unlock().

Replace deprecated CPU-hotplug functions with the official version.
The behavior remains unchanged.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>