mac80211: typo fixes in kerneldoc comments

Correct some trivial typos in kerneldoc comments.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Link: https://lore.kernel.org/r/20191024213647.5507-1-chris.packham@alliedtelesis.co.nz


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