mac80211: avoid VHT usage with no 80MHz chans allowed

Currently if 80MHz channels are not allowed for use, the VHT IE is not
included in the probe request for an AP. This is not good enough if the
AP is configured with the wrong regulatory and supports VHT even where
prohibited or in TDLS scenarios.
Mark the ifmgd with the DISABLE_VHT flag for the misbehaving-AP case, and
unset VHT support from the peer-station entry for the TDLS case.

Signed-off-by: Arik Nemtsov <arikx.nemtsov@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>