cfg80211: drop duplicated documentation of field "reg_notifier"

The field "reg_notifier" was already documented above the definition of
struct wiphy. The comment inside the definition of the struct did not
bring more information.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200221115604.594035-6-Jerome.Pouiller@silabs.com


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