As part of ongoing hotplug work, it is necessary to determine if a
given ZFS vdev matches the path of a known device being added to
the system. Since this is reported (via sysevents) in terms of a
device path (not a /dev path), it would be beneficial to have this
information in the vdev config (as opposed to some resolvepath &
strcmp kludge).
This would also help ZFS boot on devices which don't support devids
(at all or due to a buggy implementation) as we don't have the /dev
path available at the time we are mounting root.