cfg80211: fix kernel-doc notation

Update missing kernel-doc annotations and fix of related warnings
at 'make htmldocs'.

Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
Link: https://lore.kernel.org/r/20200408231013.28370-1-l.rubusch@gmail.com


[fix indentation, attribute references]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>