tty: USB does not need the filp argument in the drivers

And indeed none of them use it. Clean this up as it will make moving to a
standard open method rather easier.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/usb/serial/ch341.c b/drivers/usb/serial/ch341.c
index 2830766..8c894a7 100644
--- a/drivers/usb/serial/ch341.c
+++ b/drivers/usb/serial/ch341.c
@@ -300,8 +300,7 @@
 
 
 /* open this device, set default parameters */
-static int ch341_open(struct tty_struct *tty, struct usb_serial_port *port,
-				struct file *filp)
+static int ch341_open(struct tty_struct *tty, struct usb_serial_port *port)
 {
 	struct usb_serial *serial = port->serial;
 	struct ch341_private *priv = usb_get_serial_port_data(serial->port[0]);
@@ -333,7 +332,7 @@
 		return -EPROTO;
 	}
 
-	r = usb_serial_generic_open(tty, port, filp);
+	r = usb_serial_generic_open(tty, port);
 
 out:	return r;
 }