hwmon: (axi-fan-control) Fix possible NULL pointer dereference

axi_fan_control_irq_handler(), dependent on the private
axi_fan_control_data structure, might be called before the hwmon
device is registered. That will cause an "Unable to handle kernel
NULL pointer dereference" error.

Fixes: 8412b410 ("hwmon: Support ADI Fan Control IP")
Signed-off-by: Dragos Bogdan <dragos.bogdan@analog.com>
Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20231025132100.649499-1-nuno.sa@analog.comSigned-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/axi-fan-control.c

@@ -496,6 +496,21 @@ static int axi_fan_control_probe(struct platform_device *pdev)
 		return -ENODEV;
 	}
 
+	ret = axi_fan_control_init(ctl, pdev->dev.of_node);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to initialize device\n");
+		return ret;
+	}
+
+	ctl->hdev = devm_hwmon_device_register_with_info(&pdev->dev,
+							 name,
+							 ctl,
+							 &axi_chip_info,
+							 axi_fan_control_groups);
+
+	if (IS_ERR(ctl->hdev))
+		return PTR_ERR(ctl->hdev);
+
 	ctl->irq = platform_get_irq(pdev, 0);
 	if (ctl->irq < 0)
 		return ctl->irq;
@@ -509,19 +524,7 @@ static int axi_fan_control_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	ret = axi_fan_control_init(ctl, pdev->dev.of_node);
-	if (ret) {
-		dev_err(&pdev->dev, "Failed to initialize device\n");
-		return ret;
-	}
-
-	ctl->hdev = devm_hwmon_device_register_with_info(&pdev->dev,
-							 name,
-							 ctl,
-							 &axi_chip_info,
-							 axi_fan_control_groups);
-
-	return PTR_ERR_OR_ZERO(ctl->hdev);
+	return 0;
 }
 
 static struct platform_driver axi_fan_control_driver = {