cfg80211: merge documentations of field "debugfsdir"

The field "privid" is documented twice. Comments were more or less the
same. The patch merge them.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200221115604.594035-7-Jerome.Pouiller@silabs.com


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