dm: serial: Adjust serial_getconfig() to use proper API

All driver-model functions should have a device as the first parameter.
Update this function accordingly.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
diff --git a/drivers/serial/serial-uclass.c b/drivers/serial/serial-uclass.c
index ffcd6d1..81f1067 100644
--- a/drivers/serial/serial-uclass.c
+++ b/drivers/serial/serial-uclass.c
@@ -294,16 +294,13 @@
 		ops->setbrg(gd->cur_serial_dev, gd->baudrate);
 }
 
-int serial_getconfig(uint *config)
+int serial_getconfig(struct udevice *dev, uint *config)
 {
 	struct dm_serial_ops *ops;
 
-	if (!gd->cur_serial_dev)
-		return 0;
-
-	ops = serial_get_ops(gd->cur_serial_dev);
+	ops = serial_get_ops(dev);
 	if (ops->getconfig)
-		return ops->getconfig(gd->cur_serial_dev, config);
+		return ops->getconfig(dev, config);
 
 	return 0;
 }