ACPI: fix section mismatch in processor_core.c:acpi_processor_hotplug_notify

Fix following warning:
WARNING: vmlinux.o(.text+0x55586c): Section mismatch in reference from the function acpi_processor_hotplug_notify() to the function .cpuinit.text:acpi_processor_start()

acpi_processor_hotplug_notify() may safely reference __cpuinit
stuff as it ids defined inside an ACPI_HOTPLUG_CPU block.
So annotate it __ref to silence the warning.
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>
Signed-off-by: NLen Brown <len.brown@intel.com>

drivers/acpi/processor_core.c

@@ -881,8 +881,8 @@ int acpi_processor_device_add(acpi_handle handle, struct acpi_device **device)
 	return 0;
 }
 
-static void
-acpi_processor_hotplug_notify(acpi_handle handle, u32 event, void *data)
+static void __ref acpi_processor_hotplug_notify(acpi_handle handle,
+						u32 event, void *data)
 {
 	struct acpi_processor *pr;
 	struct acpi_device *device = NULL;