dmaengine: mpc512x: Use resource_size

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: NTobias Klauser <tklauser@distanz.ch>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

drivers/dma/mpc512x_dma.c

@@ -657,7 +657,7 @@ static int __devinit mpc_dma_probe(struct of_device *op,
 	}
 
 	regs_start = res.start;
-	regs_size = res.end - res.start + 1;
+	regs_size = resource_size(&res);
 
 	if (!devm_request_mem_region(dev, regs_start, regs_size, DRV_NAME)) {
 		dev_err(dev, "Error requesting memory region!\n");