serial: mvebu-uart: fix unused variable warning

There's a warning shows that 'ret' becomes an unused variable
after simplify the return expression of mvebu_uart_probe(). So
remove it.

Fixes: b6353702 ("serial: mvebu-uart: simplify the return expression of mvebu_uart_probe()")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Qinglang Miao <miaoqinglang@huawei.com>
Link: https://lore.kernel.org/r/20200929085651.158283-1-miaoqinglang@huawei.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/mvebu-uart.c

@@ -803,7 +803,7 @@ static int mvebu_uart_probe(struct platform_device *pdev)
 							   &pdev->dev);
 	struct uart_port *port;
 	struct mvebu_uart *mvuart;
-	int ret, id, irq;
+	int id, irq;
 
 	if (!reg) {
 		dev_err(&pdev->dev, "no registers defined\n");