platform/x86/siemens: simatic-ipc-batt: fix wrong pointer pass to PTR_ERR()

Fix wrong pointer pass to PTR_ERR() if devm_gpiod_get_index() fails.

Fixes: 917f5434 ("platform/x86: simatic-ipc: add CMOS battery monitoring")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20230809081227.1221267-1-yangyingliang@huawei.com


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