staging: dgnc: remove redundant variable null check

The unit struct(un_t) was not used in dgnc_tty_hangup().
Signed-off-by: Daeseok Youn <daeseok.youn@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/dgnc/dgnc_tty.c

@@ -1289,15 +1289,9 @@ static int dgnc_block_til_ready(struct tty_struct *tty,
  */
 static void dgnc_tty_hangup(struct tty_struct *tty)
 {
-	struct un_t	*un;
-
 	if (!tty || tty->magic != TTY_MAGIC)
 		return;
 
-	un = tty->driver_data;
-	if (!un || un->magic != DGNC_UNIT_MAGIC)
-		return;
-
 	/* flush the transmit queues */
 	dgnc_tty_flush_buffer(tty);
 }