hwmon: (gpd-fan) Fix error handling in gpd_fan_probe()

hwmon: (gpd-fan) Fix error handling in gpd_fan_probe()

devm_request_region() returns a NULL pointer on error, not an ERR_PTR().
Handle it accordingly.

Also fix error return from the call to devm_hwmon_device_register_with_info().

Fixes: 0ab88e239439 ("hwmon: add GPD devices sensor driver")
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Reviewed-by: Cryolitia PukNgae <cryolitia@uniontech.com>
Link: https://lore.kernel.org/r/20251010204447.94343-1-harshit.m.mogalapalli@oracle.com
[groeck: Updated subject to improve readability]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>