serial: sa1100: use platform_get_resource()

Use platform_get_resource() to fetch the memory resource
instead of open-coded variant.

While here, fail the probe if no resource found or no port is added.

Signed-off-by: Andy Shevchenko <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/serial/sa1100.c

···
 
 static int sa1100_serial_probe(struct platform_device *dev)
 {
-	struct resource *res = dev->resource;
+	struct resource *res;
 	int i;
 
-	for (i = 0; i < dev->num_resources; i++, res++)
-		if (res->flags & IORESOURCE_MEM)
-			break;
+	res = platform_get_resource(dev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -EINVAL;
 
-	if (i < dev->num_resources) {
-		for (i = 0; i < NR_PORTS; i++) {
-			if (sa1100_ports[i].port.mapbase != res->start)
-				continue;
-
-			sa1100_serial_add_one_port(&sa1100_ports[i], dev);
+	for (i = 0; i < NR_PORTS; i++)
+		if (sa1100_ports[i].port.mapbase == res->start)
 			break;
-		}
-	}
+	if (i == NR_PORTS)
+		return -ENODEV;
+
+	sa1100_serial_add_one_port(&sa1100_ports[i], dev);
 
 	return 0;
 }