pata_octeon_cf: Use resource_size function

Use resource_size function instead of explicit computation.
Patch found using coccinelle.
Signed-off-by: Alexandru Gheorghiu <gheorghiuandru@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/ata/pata_octeon_cf.c

@@ -926,7 +926,7 @@ static int octeon_cf_probe(struct platform_device *pdev)
 			goto free_cf_port;
 		}
 		cs1 = devm_ioremap_nocache(&pdev->dev, res_cs1->start,
-					   res_cs1->end - res_cs1->start + 1);
+					   resource_size(res_cs1));
 
 		if (!cs1)
 			goto free_cf_port;