serial: 8250_dw: Disable clock on error

If there is no clock rate for uartclk defined, disable the previously
enabled clock again.

Found by Linux Driver Verification project (linuxtesting.org).

Fixes: 23f5b3fd serial: 8250_dw: only get the clock rate in one place
Signed-off-by: Stefan Potyra <Stefan.Potyra@elektrobit.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_dw.c

@@ -515,7 +515,8 @@ static int dw8250_probe(struct platform_device *pdev)
 	/* If no clock rate is defined, fail. */
 	if (!p->uartclk) {
 		dev_err(dev, "clock rate not defined\n");
-		return -EINVAL;
+		err = -EINVAL;
+		goto err_clk;
 	}
 
 	data->pclk = devm_clk_get(dev, "apb_pclk");