mxser: remove unnesesary NULL check

mxser_transmit_chars(tty, port) is called only from mxser_interrupt().
NULL check is performed in mxser_interrupt() so it is redundant here.
Signed-off-by: Kulikov Vasiliy <segooon@gmail.com>
Acked-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/char/mxser.c

@@ -2193,7 +2193,7 @@ static void mxser_transmit_chars(struct tty_struct *tty, struct mxser_port *port
 	port->mon_data.up_txcnt += (cnt - port->xmit_cnt);
 	port->icount.tx += (cnt - port->xmit_cnt);
 
-	if (port->xmit_cnt < WAKEUP_CHARS && tty)
+	if (port->xmit_cnt < WAKEUP_CHARS)
 		tty_wakeup(tty);
 
 	if (port->xmit_cnt <= 0) {