wm97xx_battery: Handle missing platform data gracefully

Don't unconditionally dereference the WM97xx core platform data since
it may not be present, causing an oops.

Signed-off-by: Mark Brown <[e-mail]>
Signed-off-by: Anton Vorontsov <[e-mail]>

drivers/power/wm97xx_battery.c

···
 		dev_err(&dev->dev, "Do not pass platform_data through "
 			"wm97xx_bat_set_pdata!\n");
 		return -EINVAL;
-	} else
-		pdata = wmdata->batt_pdata;
+	}
+
+	if (!wmdata) {
+		dev_err(&dev->dev, "No platform data supplied\n");
+		return -EINVAL;
+	}
+
+	pdata = wmdata->batt_pdata;
 
 	if (dev->id != -1)
 		return -EINVAL;