power: reset: xgene-reboot: Use devm_platform_ioremap_resource() helper

Use device life-cycle managed ioremap function to simplify probe and
exit paths.

While here add __iomem to the returned pointer to fix a sparse warning.
Signed-off-by: Andrew Davis <afd@ti.com>
Link: https://lore.kernel.org/r/20240212162831.67838-4-afd@ti.comSigned-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/reset/xgene-reboot.c

@@ -22,7 +22,7 @@
 
 struct xgene_reboot_context {
 	struct device *dev;
-	void *csr;
+	void __iomem *csr;
 	u32 mask;
 	struct notifier_block restart_handler;
 };
@@ -54,7 +54,7 @@ static int xgene_reboot_probe(struct platform_device *pdev)
 	if (!ctx)
 		return -ENOMEM;
 
-	ctx->csr = of_iomap(dev->of_node, 0);
+	ctx->csr = devm_platform_ioremap_resource(pdev, 0);
 	if (!ctx->csr) {
 		dev_err(dev, "can not map resource\n");
 		return -ENODEV;
@@ -67,10 +67,8 @@ static int xgene_reboot_probe(struct platform_device *pdev)
 	ctx->restart_handler.notifier_call = xgene_restart_handler;
 	ctx->restart_handler.priority = 128;
 	err = register_restart_handler(&ctx->restart_handler);
-	if (err) {
-		iounmap(ctx->csr);
+	if (err)
 		dev_err(dev, "cannot register restart handler (err=%d)\n", err);
-	}
 
 	return err;
 }