usb-serial: handle NULL termios methods as "no hardware changing support"

Signed-off-by: NAlan Cox <alan@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/usb-serial.c

@@ -429,6 +429,8 @@ static void serial_set_termios (struct tty_struct *tty, struct ktermios * old)
 	/* pass on to the driver specific version of this function if it is available */
 	if (port->serial->type->set_termios)
 		port->serial->type->set_termios(port, old);
+	else
+		tty_termios_copy_hw(tty->termios, old);
 }
 
 static void serial_break (struct tty_struct *tty, int break_state)