wireless: radiotap: fix some kernel-doc

The vendor namespaces argument isn't described here, add it.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Link: https://lore.kernel.org/r/20200924192511.2bf5cc761d3a.I9b4579ab3eebe3d7889b59eea8fa50d683611bab@changeid


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