UML: Remove unused variable from line driver

Signed-off-by: Jan Kiszka <jan.kiszka@web.de>
Acked-by: WANG Cong <xiyou.wangcong@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

arch/um/drivers/line.c

@@ -18,7 +18,6 @@ static irqreturn_t line_interrupt(int irq, void *data)
 {
 	struct chan *chan = data;
 	struct line *line = chan->line;
-	struct tty_struct *tty;
 
 	if (line)
 		chan_interrupt(&line->chan_list, &line->task, line->tty, irq);