Fix bogus warning in sysdev_driver_register()

        if ((drv->entry.next != drv->entry.prev) ||
            (drv->entry.next != NULL)) {

warns list_empty(&drv->entry).

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Greg KH <gregkh@suse.de>
Cc: Len Brown <lenb@kernel.org>
[ Version 2 totally redone based on suggestions from Linus & Greg ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/base/sys.c

@@ -175,8 +175,7 @@ int sysdev_driver_register(struct sysdev_class *cls, struct sysdev_driver *drv)
 	}
 
 	/* Check whether this driver has already been added to a class. */
-	if ((drv->entry.next != drv->entry.prev) ||
-	    (drv->entry.next != NULL)) {
+	if (drv->entry.next && !list_empty(&drv->entry)) {
 		printk(KERN_WARNING "sysdev: class %s: driver (%p) has already"
 			" been registered to a class, something is wrong, but "
 			"will forge on!\n", cls->name, drv);