serial: 8250_uniphier: fix error return code in uniphier_uart_probe()

Fix to return a negative error code from the port register error
handling case instead of 0, as done elsewhere in this function.

Fixes: 39be40ce066d ("serial: 8250_uniphier: fix serial port index in private data")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_uniphier.c

@@ -250,12 +250,13 @@ static int uniphier_uart_probe(struct platform_device *pdev)
 	up.dl_read = uniphier_serial_dl_read;
 	up.dl_write = uniphier_serial_dl_write;
 
-	priv->line = serial8250_register_8250_port(&up);
-	if (priv->line < 0) {
+	ret = serial8250_register_8250_port(&up);
+	if (ret < 0) {
 		dev_err(dev, "failed to register 8250 port\n");
 		clk_disable_unprepare(priv->clk);
 		return ret;
 	}
+	priv->line = ret;
 
 	platform_set_drvdata(pdev, priv);