USB: serial: fix console error reporting

Do not report errors in write path if port is used as a console as this
may trigger the same error (and error report) resulting in a loop.
Reported-by: NStephen Hemminger <shemminger@vyatta.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: NJohan Hovold <jhovold@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/serial/generic.c

@@ -217,8 +217,10 @@ static int usb_serial_generic_write_start(struct usb_serial_port *port)
 	clear_bit(i, &port->write_urbs_free);
 	result = usb_submit_urb(urb, GFP_ATOMIC);
 	if (result) {
-		dev_err(&port->dev, "%s - error submitting urb: %d\n",
+		if (!port->port.console) {
+			dev_err(&port->dev, "%s - error submitting urb: %d\n",
 						__func__, result);
+		}
 		set_bit(i, &port->write_urbs_free);
 		spin_lock_irqsave(&port->lock, flags);
 		port->tx_bytes -= count;