usb: Bind devices to ACPI devices when possible

Built-in USB devices will typically have a representation in the system
ACPI tables. Add support for binding the two together so the USB code can
make use of the associated methods.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/core/usb.h b/drivers/usb/core/usb.h
index 71648dc..5c5c538 100644
--- a/drivers/usb/core/usb.h
+++ b/drivers/usb/core/usb.h
@@ -156,3 +156,10 @@
 extern void usb_notify_add_bus(struct usb_bus *ubus);
 extern void usb_notify_remove_bus(struct usb_bus *ubus);
 
+#ifdef CONFIG_ACPI
+extern int usb_acpi_register(void);
+extern void usb_acpi_unregister(void);
+#else
+static inline int usb_acpi_register(void) { return 0; };
+static inline void usb_acpi_unregister(void) { };
+#endif