ACPI: Add weak routines for ACPI CPU Hotplug

Add weak functions for architectures which do not support
hot-adding and removing CPUs which aren't detected at
bootup. (e.g. via MADT).

This helps preserve the Kconfig dependency from:

commit cbfc1bae ("[ACPI] ACPI_HOTPLUG_CPU Kconfig dependency
update")

    prevent:

    HOTPLUG_CPU=y
    ACPI_PROCESSOR=y
    ACPI_HOTPLUG_CPU=n
Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/acpi_processor.c

@@ -164,6 +164,24 @@ static int acpi_processor_errata(void)
    -------------------------------------------------------------------------- */
 
 #ifdef CONFIG_ACPI_HOTPLUG_CPU
+int __weak acpi_map_cpu(acpi_handle handle,
+		phys_cpuid_t physid, int *pcpu)
+{
+	return -ENODEV;
+}
+
+int __weak acpi_unmap_cpu(int cpu)
+{
+	return -ENODEV;
+}
+
+int __weak arch_register_cpu(int cpu)
+{
+	return -ENODEV;
+}
+
+void __weak arch_unregister_cpu(int cpu) {}
+
 static int acpi_processor_hotadd_init(struct acpi_processor *pr)
 {
 	unsigned long long sta;