tty: tty_ldisc: Do not use assignment in if condition

Do not use assignment in if condition following the advice of
checkpatch.pl.

Signed-off-by: Xiaofei Tan <tanxiaofei@huawei.com>
Link: https://lore.kernel.org/r/1617779210-51576-10-git-send-email-tanxiaofei@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/tty_ldisc.c

@@ -508,7 +508,8 @@ static int tty_ldisc_failto(struct tty_struct *tty, int ld)
 		return PTR_ERR(disc);
 	tty->ldisc = disc;
 	tty_set_termios_ldisc(tty, ld);
-	if ((r = tty_ldisc_open(tty, disc)) < 0)
+	r = tty_ldisc_open(tty, disc);
+	if (r < 0)
 		tty_ldisc_put(disc);
 	return r;
 }