USB: ratelimit debounce error messages

flaky hardware can cause a lot of debounce failed messages. To limit
the performance impact, a ratelimit should be used.
Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/core/hub.c

@@ -2443,7 +2443,7 @@ static void hub_port_connect_change(struct usb_hub *hub, int port1,
 
 	if (portchange & USB_PORT_STAT_C_CONNECTION) {
 		status = hub_port_debounce(hub, port1);
-		if (status < 0) {
+		if (status < 0 && printk_ratelimit()) {
 			dev_err (hub_dev,
 				"connect-debounce failed, port %d disabled\n",
 				port1);