platform/x86: huawei-wmi: check the return value of device_create_file()

The function device_create_file() in huawei_wmi_battery_add() can fail,
so its return value should be checked.

Fixes: 355a070b ("platform/x86: huawei-wmi: Add battery charging thresholds")
Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Link: https://lore.kernel.org/r/20220303022421.313-1-baijiaju1990@gmail.com


Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>