[driver model] Remove struct sys_device::entry

It was added by accident from another patch and is redundant with 
struct sys_device::kobj.entry.

drivers/base/sys.c

@@ -218,9 +218,6 @@ void sys_device_unregister(struct sys_device * sysdev)
 		if (drv->remove)
 			drv->remove(sysdev);
 	}
-
-	list_del_init(&sysdev->entry);
-
 	up_write(&system_subsys.rwsem);
 
 	kobject_unregister(&sysdev->kobj);

include/linux/sysdev.h

@@ -72,7 +72,6 @@ struct sys_device {
 	u32		id;
 	struct sysdev_class	* cls;
 	struct kobject		kobj;
-	struct list_head	entry;
 };
 
 extern int sys_device_register(struct sys_device *);