device: fix segfault when recreating devices

device: fix segfault when recreating devices

Depending on the configuration, the callback on device_release could end up
deleting the device_dep from the list. If that happens, it must not be added
back to the recreated device, since that leads to use-after-free issues.
Check dep->dev before adding it back.

Signed-off-by: Felix Fietkau <nbd@nbd.name>