xen-balloon: convert sysdev_class to a regular subsystem

After all sysdev classes are ported to regular driver core entities, the
sysdev implementation will be entirely removed from the kernel.

Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/include/xen/balloon.h b/include/xen/balloon.h
index d29c153..cc2e1a7 100644
--- a/include/xen/balloon.h
+++ b/include/xen/balloon.h
@@ -29,11 +29,11 @@
 		bool highmem);
 void free_xenballooned_pages(int nr_pages, struct page **pages);
 
-struct sys_device;
+struct device;
 #ifdef CONFIG_XEN_SELFBALLOONING
-extern int register_xen_selfballooning(struct sys_device *sysdev);
+extern int register_xen_selfballooning(struct device *dev);
 #else
-static inline int register_xen_selfballooning(struct sys_device *sysdev)
+static inline int register_xen_selfballooning(struct device *dev)
 {
 	return -ENOSYS;
 }