USB: adding comment for ipaq forcing number of ports

The reason for forcing a number of ports should be documented.
Signed-off-by: NOliver Neukum <oneukum@suse.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/ipaq.c

@@ -570,6 +570,11 @@ static struct usb_serial_driver ipaq_device = {
 	.description =		"PocketPC PDA",
 	.usb_driver = 		&ipaq_driver,
 	.id_table =		ipaq_id_table,
+	/*
+	 * some devices have an extra endpoint, which
+	 * must be ignored as it would make the core
+	 * create a second port which oopses when used
+	 */
 	.num_ports =		1,
 	.open =			ipaq_open,
 	.close =		ipaq_close,