omap: rng: Use resource_size instead of manual calculation

Use the resource_size function instead of manually calculating the
resource size. This reduces the chance of introducing off-by-one-errors.

Signed-off-by: Tobias Klauser <[e-mail]>

drivers/char/hw_random/omap-rng.c

···
 	if (!res)
 		return -ENOENT;
 
-	mem = request_mem_region(res->start, res->end - res->start + 1,
+	mem = request_mem_region(res->start, resource_size(res),
 				 pdev->name);
 	if (mem == NULL) {
 		ret = -EBUSY;
···
 	}
 
 	dev_set_drvdata(&pdev->dev, mem);
-	rng_base = ioremap(res->start, res->end - res->start + 1);
+	rng_base = ioremap(res->start, resource_size(res));
 	if (!rng_base) {
 		ret = -ENOMEM;
 		goto err_ioremap;