mailbox: hi3660: Make use of the helper function devm_platform_ioremap_resource()

Use the devm_platform_ioremap_resource() helper instead of
calling platform_get_resource() and devm_ioremap_resource()
separately

Signed-off-by: Cai Huoqing <[e-mail]>
Signed-off-by: Jassi Brar <[e-mail]>

drivers/mailbox/hi3660-mailbox.c

···
 	struct device *dev = &pdev->dev;
 	struct hi3660_mbox *mbox;
 	struct mbox_chan *chan;
-	struct resource *res;
 	unsigned long ch;
 	int err;
 
···
 	if (!mbox)
 		return -ENOMEM;
 
-	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-	mbox->base = devm_ioremap_resource(dev, res);
+	mbox->base = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(mbox->base))
 		return PTR_ERR(mbox->base);