platform/x86: dell/dell-rbtn: Check ACPI_COMPANION() against NULL

Every platform driver can be forced to match a device that doesn't match
its list of device IDs because of device_match_driver_override(), so
platform drivers that rely on the existence of a device's ACPI companion
object need to verify its presence.

Accordingly, add a requisite ACPI_COMPANION() check against NULL to the
platform/x86 dell-rbtn driver.

Fixes: 19ebacf ("platform/x86: dell/dell-rbtn: Convert ACPI driver to a platform one")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://patch.msgid.link/2276487.irdbgypaU6@rafael.j.wysocki
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

Author: rafaeljw

drivers/platform/x86/dell/dell-rbtn.c

@@ -396,11 +396,15 @@ static void rbtn_cleanup(struct device *dev)
 
 static int rbtn_probe(struct platform_device *pdev)
 {
-	struct acpi_device *device = ACPI_COMPANION(&pdev->dev);
 	struct rbtn_data *rbtn_data;
+	struct acpi_device *device;
 	enum rbtn_type type;
 	int ret = 0;
 
+	device = ACPI_COMPANION(&pdev->dev);
+	if (!device)
+		return -ENODEV;
+
 	type = rbtn_check(device);
 	if (type == RBTN_UNKNOWN) {
 		dev_info(&pdev->dev, "Unknown device type\n");