wifi: cfg80211: improve documentation for flag fields

Fix and hopefully improve documentation for 'flag' fields of
a few types by adding references to relevant enumerations.

Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Link: https://lore.kernel.org/r/20230713132957.275859-1-dmantipov@yandex.ru


Signed-off-by: Johannes Berg <johannes.berg@intel.com>