linuxkpi: Fix a lock leak in lkpi_sta_scan_to_auth()

PR: 283015
Reviewed by: bz
MFC after: 1 week
Fixes: 0936c648ad0e ("LinuxKPI: 802.11: update the ni/lsta reference cycle")
Differential Revision: https://reviews.freebsd.org/D47949

(cherry picked from commit 926905796749750da6464b97ec4f8eec0882cc0e)