serial: pch_uart: fix tty-kref leak in rx-error path

Fix tty-kref leak introduced by commit 384e301 ("pch_uart: fix a
deadlock when pch_uart as console") which never put its tty reference.

Cc: stable@vger.kernel.org
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/pch_uart.c

@@ -1098,6 +1098,8 @@ static void pch_uart_err_ir(struct eg20t_port *priv, unsigned int lsr)
 	if (tty == NULL) {
 		for (i = 0; error_msg[i] != NULL; i++)
 			dev_err(&priv->pdev->dev, error_msg[i]);
+	} else {
+		tty_kref_put(tty);
 	}
 }