mac80211: use common radiotap code for cooked monitors

There's no need to hardcode a subset of the
radiotap header for cooked monitor receive,
we can just reuse the normal monitor mode
radiotap code. This simplifies the code and
extends the information available on cooked
monitor interfaces.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>