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/keyspan.c b/drivers/usb/serial/keyspan.c
index 2594b87..f8c4b07 100644
--- a/drivers/usb/serial/keyspan.c
+++ b/drivers/usb/serial/keyspan.c
@@ -1209,8 +1209,7 @@
 }
 
 
-static int keyspan_open(struct tty_struct *tty,
-			struct usb_serial_port *port, struct file *filp)
+static int keyspan_open(struct tty_struct *tty, struct usb_serial_port *port)
 {
 	struct keyspan_port_private 	*p_priv;
 	struct keyspan_serial_private 	*s_priv;