nl80211: limit band information in non-split data

In non-split data, we shouldn't be adding S1G and 6 GHz
data (or future bands) since we're really close to the
4k message size limit. Remove those bands, any modern
userspace that can use S1G or 6 GHz should already be
using split dumps, and if not then it needs to update.

Link: https://lore.kernel.org/r/20210712215329.31444162a2c2.I5555312e4a074c84f8b4e7ad79dc4d1fbfc5126c@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>