i2c-s3c2410: use resource_size()

Change the usage of res->end-res->start to resource_size(), missed
by the last patch to change this.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
diff --git a/drivers/i2c/busses/i2c-s3c2410.c b/drivers/i2c/busses/i2c-s3c2410.c
index 079a312..8f42a45 100644
--- a/drivers/i2c/busses/i2c-s3c2410.c
+++ b/drivers/i2c/busses/i2c-s3c2410.c
@@ -828,7 +828,7 @@
 		goto err_clk;
 	}
 
-	i2c->ioarea = request_mem_region(res->start, (res->end-res->start)+1,
+	i2c->ioarea = request_mem_region(res->start, resource_size(res),
 					 pdev->name);
 
 	if (i2c->ioarea == NULL) {
@@ -837,7 +837,7 @@
 		goto err_clk;
 	}
 
-	i2c->regs = ioremap(res->start, (res->end-res->start)+1);
+	i2c->regs = ioremap(res->start, resource_size(res));
 
 	if (i2c->regs == NULL) {
 		dev_err(&pdev->dev, "cannot map IO\n");