if_put after if_get.
if_put after if_get.

this is a bit funky cos we give up the ref while sleeping in tunread,
and have to get a new ref on wakeup.

ok claudio@

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