When the device is attached, immediately create the timedelta sensor with the SENSOR_FINVALID flag set and without a description.  We do not need a dummy description as a sensor with the FINVALID flags set will not show up or be used anyways.  It's merely an indication to applications that there is a sensor that will eventually have a correct value.
When the device is attached, immediately create the timedelta sensor with the
SENSOR_FINVALID flag set and without a description.  We do not need a dummy
description as a sensor with the FINVALID flags set will not show up or be used
anyways.  It's merely an indication to applications that there is a sensor that
will eventually have a correct value.

The SENSOR_FINVALID flag is removed and the description is set to the proper
clockname as soon as we have received the first valid time information.

This enables ntpd to check for hotplug events and rescan the list of timedelta
sensors after a hotplug event.

discussed with deraadt.

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars