serial: sccnxp: Fix error handling in sccnxp_probe()

commit c9126143 upstream.

sccnxp_probe() returns result of regulator_disable() that may lead
to returning zero, while device is not properly initialized.
Also the driver enables clocks, but it does not disable it.

Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Cc: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/sccnxp.c

@@ -889,7 +889,16 @@ static int sccnxp_probe(struct platform_device *pdev)
 			goto err_out;
 		uartclk = 0;
 	} else {
-		clk_prepare_enable(clk);
+		ret = clk_prepare_enable(clk);
+		if (ret)
+			goto err_out;
+
+		ret = devm_add_action_or_reset(&pdev->dev,
+				(void(*)(void *))clk_disable_unprepare,
+				clk);
+		if (ret)
+			goto err_out;
+
 		uartclk = clk_get_rate(clk);
 	}
 
@@ -988,7 +997,7 @@ static int sccnxp_probe(struct platform_device *pdev)
 	uart_unregister_driver(&s->uart);
 err_out:
 	if (!IS_ERR(s->regulator))
-		return regulator_disable(s->regulator);
+		regulator_disable(s->regulator);
 
 	return ret;
 }