tty: moxa, fix refcounting in moxa_poll_port

There is missing tty_kref_put on some paths in moxa_poll_port,
although the reference is always taken. Fix it.
Signed-off-by: NJiri Slaby <jirislaby@gmail.com>
Reported-by: NJan 'Yenya' Kasprzak <kas@fi.muni.cz>
Signed-off-by: NAlan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/char/moxa.c

@@ -1486,11 +1486,11 @@ static int moxa_poll_port(struct moxa_port *p, unsigned int handle,
 	}
 
 	if (!handle) /* nothing else to do */
-		return 0;
+		goto put;
 
 	intr = readw(ip); /* port irq status */
 	if (intr == 0)
-		return 0;
+		goto put;
 
 	writew(0, ip); /* ACK port */
 	ofsAddr = p->tableAddr;
@@ -1499,16 +1499,17 @@ static int moxa_poll_port(struct moxa_port *p, unsigned int handle,
 				ofsAddr + HostStat);
 
 	if (!inited)
-		return 0;
+		goto put;
 
 	if (tty && (intr & IntrBreak) && !I_IGNBRK(tty)) { /* BREAK */
 		tty_insert_flip_char(tty, 0, TTY_BREAK);
 		tty_schedule_flip(tty);
 	}
-	tty_kref_put(tty);
 
 	if (intr & IntrLine)
 		moxa_new_dcdstate(p, readb(ofsAddr + FlagStat) & DCD_state);
+put:
+	tty_kref_put(tty);
 
 	return 0;
 }