Input: serio - support multiple child devices per single parent

Some (rare) serio devices need to have multiple serio children. One of
the examples is PS/2 multiplexer present on several TQC STKxxx boards,
which connect PS/2 keyboard and mouse to single tty port.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/drivers/input/mouse/psmouse-base.c b/drivers/input/mouse/psmouse-base.c
index 73a7af2..cd9d0c9 100644
--- a/drivers/input/mouse/psmouse-base.c
+++ b/drivers/input/mouse/psmouse-base.c
@@ -1584,10 +1584,10 @@
 	if (!new_dev)
 		return -ENOMEM;
 
-	while (serio->child) {
+	while (!list_empty(&serio->children)) {
 		if (++retry > 3) {
 			printk(KERN_WARNING
-				"psmouse: failed to destroy child port, "
+				"psmouse: failed to destroy children ports, "
 				"protocol change aborted.\n");
 			input_free_device(new_dev);
 			return -EIO;