[PATCH] Remove comment about IEEE80211_RADIOTAP_FCS

IEEE80211_RADIOTAP_FCS is obsolete and should not be used.  It's no
longer defined.  Remove it from the comment too.

Signed-off-by: Pavel Roskin <proski@gnu.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>