ACPI / PM: acpi_processor_suspend() can be static

Since acpi_processor_suspend() and acpi_processor_resume() need not
be visible outside of the file they are defined in, make them
static.

[rjw: Changelog]
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>