platform/x86: fujitsu-tablet: 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 requisite ACPI_COMPANION() checks against NULL to the
platform/x86 fujitsu-tablet driver.

Fixes: bd13b26 ("platform/x86: fujitsu-tablet: 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/10861611.nUPlyArG6x@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/fujitsu-tablet.c

@@ -445,10 +445,14 @@ static acpi_status fujitsu_walk_resources(struct acpi_resource *res, void *data)
 
 static int acpi_fujitsu_probe(struct platform_device *pdev)
 {
-	struct acpi_device *adev = ACPI_COMPANION(&pdev->dev);
+	struct acpi_device *adev;
 	acpi_status status;
 	int error;
 
+	adev = ACPI_COMPANION(&pdev->dev);
+	if (!adev)
+		return -ENODEV;
+
 	status = acpi_walk_resources(adev->handle, METHOD_NAME__CRS,
 			fujitsu_walk_resources, NULL);
 	if (ACPI_FAILURE(status) || !fujitsu.irq || !fujitsu.io_base)