core/device: always accept syspath change

core/device: always accept syspath change

When multiple devices have the same devlink, then
adding/updating/removing one of the device may cause syspath change.

Fixes the following issue in
https://github.com/systemd/systemd/issues/23208#issue-1217909746
> the above shows an inconsistency between udev's and systemd's handling
> of the two different devices having the same alias. While udev replaces
> the by-uuid symlink which now points to sdh1 rather than sdd1, systemd
> keeps the previous mapping to sdd1 and emits a warning. This is not the
> problem cause but worth mentioning.