USB: quatech2: Staticize local symbol

'qt2_process_read_urb' is referenced only in this file. Make it static.
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/serial/quatech2.c

@@ -523,7 +523,7 @@ static void qt2_process_flush(struct usb_serial_port *port, unsigned char *ch)
 	return;
 }
 
-void qt2_process_read_urb(struct urb *urb)
+static void qt2_process_read_urb(struct urb *urb)
 {
 	struct usb_serial *serial;
 	struct qt2_serial_private *serial_priv;