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/mos7840.c b/drivers/usb/serial/mos7840.c
index b93f0f9..f11abf5 100644
--- a/drivers/usb/serial/mos7840.c
+++ b/drivers/usb/serial/mos7840.c
@@ -824,8 +824,7 @@
  *	Otherwise we return a negative error number.
  *****************************************************************************/
 
-static int mos7840_open(struct tty_struct *tty,
-			struct usb_serial_port *port, struct file *filp)
+static int mos7840_open(struct tty_struct *tty, struct usb_serial_port *port)
 {
 	int response;
 	int j;