LinuxKPI: 802.11: plug a ni leak in lkpi_sta_assoc_to_run()

In lkpi_sta_assoc_to_run() we are going through some code segments
twice (auth->assoc, assoc->authorized). The 2nd time we shall not
re-gain a reference on the net80211 node as otherwise it'll leak.
Likewise we do not have to re-set lsta and sta.

Sponsored by: The FreeBSD Foundation
MFC after: 3 days