LinuxKPI: 802.11: error on state transition failure

The state transition failures we were seeing in the early days are
solved. If we now experience one stop processing before passing
over to net80211 (sta_newstate()) and before updating iv_state on
the vap.

Sponsored by: The FreeBSD Foundation
MFC after: 3 days
Reviewed by: cc
Differential Revision: https://reviews.freebsd.org/D42423