LinuxKPI: 802.11: change ic_parent() to not call mo_stop()/mo_start()

Driven by net80211 we may call mac80211 ops stop() and start() mostly
when toggling a first VAP. While this is FreeBSD behaviour the firmware
based LinuxKPI drivers seem to possibly clear state in the case of stop()
triggering further errors down the line.
We call mo_start() when starting the VAP and mo_stop() when destroying
it now only. In the future (e.g., in multi-VAP setups) we may need to
re-address some of this so keep the code under #ifdef.

Sponsored by: The FreeBSD Foundation
MFC after: 3 days