gpio: sim: lock hog configfs items if present

Depending on the user config, the leaf entry may be the hog directory,
not line. Check it and lock the correct item.

Fixes: 8bd76b3d ("gpio: sim: lock up configfs that an instantiated device depends on")
Tested-by: Koichiro Den <koichiro.den@canonical.com>
Link: https://lore.kernel.org/r/20250203110123.87701-1-brgl@bgdev.pl


Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>