cfg80211: drop duplicated documentation of field "perm_addr"

The field "perm_addr" was already documented above the definition of
struct wiphy. Comments were almost identical.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200221115604.594035-5-Jerome.Pouiller@silabs.com


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