USB: fix dev_dbg() call in visor.c

Turns out that this macro doesn't work in usb-serial drivers, I had forgotten
about that :(
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

drivers/usb/serial/visor.c

@@ -494,7 +494,7 @@ static int visor_write (struct usb_serial_port *port, const unsigned char *buf,
 	spin_lock_irqsave(&priv->lock, flags);
 	if (priv->outstanding_urbs > URB_UPPER_LIMIT) {
 		spin_unlock_irqrestore(&priv->lock, flags);
-		dev_dbg(&port->dev, "write limit hit\n");
+		dbg("%s - write limit hit\n", __FUNCTION__);
 		return 0;
 	}
 	spin_unlock_irqrestore(&priv->lock, flags);