xen/acpi: ACPI cpu hotplug

This patch implement real Xen ACPI cpu hotplug driver as module.
When loaded, it replaces Xen stub driver.

For booting existed cpus, the driver enumerates them.
For hotadded cpus, which added at runtime and notify OS via
device or container event, the driver is invoked to add them,
parsing cpu information, hypercalling to Xen hypervisor to add
them, and finally setting up new /sys interface for them.

Signed-off-by: Liu Jinsong <jinsong.liu@intel.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

include/xen/acpi.h

@@ -54,6 +54,9 @@ void xen_stub_memory_device_exit(void);
 int xen_stub_processor_init(void);
 void xen_stub_processor_exit(void);
 
+void xen_pcpu_hotplug_sync(void);
+int xen_pcpu_id(uint32_t acpi_id);
+
 int xen_acpi_notify_hypervisor_state(u8 sleep_state,
 				     u32 pm1a_cnt, u32 pm1b_cnd);