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>

drivers/usb/serial/generic.c

@@ -114,8 +114,7 @@ void usb_serial_generic_deregister(void)
 #endif
 }
 
-int usb_serial_generic_open(struct tty_struct *tty,
-			struct usb_serial_port *port, struct file *filp)
+int usb_serial_generic_open(struct tty_struct *tty, struct usb_serial_port *port)
 {
 	struct usb_serial *serial = port->serial;
 	int result = 0;