ACPI / processor: make function acpi_processor_check_duplicates() static

The function acpi_processor_check_duplicates() is local to the source
and does not need to be in global scope, so make it static.

Cleans up sparse warnings:
symbol 'acpi_processor_check_duplicates' was not declared. Should it
be static?
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/acpi_processor.c

@@ -670,7 +670,7 @@ static acpi_status __init acpi_processor_ids_walk(acpi_handle handle,
 
 }
 
-void __init acpi_processor_check_duplicates(void)
+static void __init acpi_processor_check_duplicates(void)
 {
 	/* check the correctness for all processors in ACPI namespace */
 	acpi_walk_namespace(ACPI_TYPE_PROCESSOR, ACPI_ROOT_OBJECT,