nl80211: remove radar information

The wiphy information is getting very close to being too
much for a typical netlink dump message and adding the
radar attributes to channels and interface combinations
can push it over the limit, which means userspace gets no
information whatsoever. Therefore, remove these again for
now, no driver actually supports radar detection anyway
and a modified userspace is required as well.

We're working on a solution that will allow userspace to
request splitting the information across multiple netlink
messages, which will allow us to add this back.

Cc: Simon Wunderlich <simon.wunderlich@s2003.tu-chemnitz.de>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>