serial: 8250-mtk: Fix reference leak in mtk8250_probe

[ Upstream commit 6e4e636 ]

The pm_runtime_enable will increase power disable depth.
Thus a pairing decrement is needed on the error handling
path to keep it balanced according to context.

Fixes: e32a83c ("serial: 8250-mtk: modify mtk uart power and clock management")
Signed-off-by: Zhang Qilong <zhangqilong3@huawei.com>
Link: https://lore.kernel.org/r/20201119141126.168850-1-zhangqilong3@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/tty/serial/8250/8250_mtk.c

@@ -572,15 +572,22 @@ static int mtk8250_probe(struct platform_device *pdev)
 	pm_runtime_enable(&pdev->dev);
 	err = mtk8250_runtime_resume(&pdev->dev);
 	if (err)
-		return err;
+		goto err_pm_disable;
 
 	data->line = serial8250_register_8250_port(&uart);
-	if (data->line < 0)
-		return data->line;
+	if (data->line < 0) {
+		err = data->line;
+		goto err_pm_disable;
+	}
 
 	data->rx_wakeup_irq = platform_get_irq_optional(pdev, 1);
 
 	return 0;
+
+err_pm_disable:
+	pm_runtime_disable(&pdev->dev);
+
+	return err;
 }
 
 static int mtk8250_remove(struct platform_device *pdev)