mailbox: armada-37xx-rwtm: convert to devm_platform_ioremap_resource

Use devm_platform_ioremap_resource() to simplify code.
Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>

drivers/mailbox/armada-37xx-rwtm-mailbox.c

@@ -143,7 +143,6 @@ static const struct mbox_chan_ops a37xx_mbox_ops = {
 static int armada_37xx_mbox_probe(struct platform_device *pdev)
 {
 	struct a37xx_mbox *mbox;
-	struct resource *regs;
 	struct mbox_chan *chans;
 	int ret;
 
@@ -156,9 +155,7 @@ static int armada_37xx_mbox_probe(struct platform_device *pdev)
 	if (!chans)
 		return -ENOMEM;
 
-	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-
-	mbox->base = devm_ioremap_resource(&pdev->dev, regs);
+	mbox->base = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(mbox->base)) {
 		dev_err(&pdev->dev, "ioremap failed\n");
 		return PTR_ERR(mbox->base);