strip: Fix termios assumption

Strip assumes that the tty drivers always have a set_termios method which
may not be true. Check this when binding to the tty so that we don't oops
later.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/net/wireless/strip.c

@@ -2611,7 +2611,7 @@ static int strip_open(struct tty_struct *tty)
 	 * We need a write method.
 	 */
 
-	if (tty->ops->write == NULL)
+	if (tty->ops->write == NULL || tty->ops->set_termios == NULL)
 		return -EOPNOTSUPP;
 
 	/*