irqchip/gic-v5: iwb: Fix iounmap probe failure path

The 0-day bot reported that on the failure path the driver iounmap()s IWB
resources that are managed through devm_ioremap(), which is clearly wrong
because the driver would end up unmapping the MMIO resource twice on
probing failure.

Fix this by removing the error path altogether and by letting devres manage
the iounmapping on clean-up.

Fixes: 695949d8b16f ("irqchip/gic-v5: Add GICv5 IWB support")
Reported-by: kernel test robot <[e-mail]>
Signed-off-by: Lorenzo Pieralisi <[e-mail]>
Signed-off-by: Thomas Gleixner <[e-mail]>
Reviewed-by: Marc Zyngier <[e-mail]>
Link: https://lore.kernel.org/all/[e-mail]
Closes: https://lore.kernel.org/oe-kbuild-all/[e-mail]

drivers/irqchip/irq-gic-v5-iwb.c

···
 	struct gicv5_iwb_chip_data *iwb_node;
 	void __iomem *iwb_base;
 	struct resource *res;
-	int ret;
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	if (!res)
···
 	}
 
 	iwb_node = gicv5_iwb_init_bases(iwb_base, pdev);
-	if (IS_ERR(iwb_node)) {
-		ret = PTR_ERR(iwb_node);
-		goto out_unmap;
-	}
+	if (IS_ERR(iwb_node))
+		return PTR_ERR(iwb_node);
 
 	return 0;
-
-out_unmap:
-	iounmap(iwb_base);
-	return ret;
 }
 
 static const struct of_device_id gicv5_iwb_of_match[] = {