hwmon: (ibmpex) Fix possible UAF when ibmpex_register_bmc() fails

Smatch report warning as follows:

drivers/hwmon/ibmpex.c:509 ibmpex_register_bmc() warn:
  '&data->list' not removed from list

If ibmpex_find_sensors() fails in ibmpex_register_bmc(), data will
be freed, but data->list will not be removed from driver_data.bmc_data,
then list traversal may cause UAF.

Fix by removeing it from driver_data.bmc_data before free().

Fixes: 57c7c3a0fd ("hwmon: IBM power meter driver")
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Link: https://lore.kernel.org/r/20221117034423.2935739-1-cuigaosheng1@huawei.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/ibmpex.c

@@ -502,6 +502,7 @@ static void ibmpex_register_bmc(int iface, struct device *dev)
 	return;
 
 out_register:
+	list_del(&data->list);
 	hwmon_device_unregister(data->hwmon_dev);
 out_user:
 	ipmi_destroy_user(data->user);