mac80211: fix broken use of VHT/20Mhz with some APs

mac80211: fix broken use of VHT/20Mhz with some APs

commit "mac80211: disable 40MHz support in case of 20MHz AP"
broke working VHT in 20Mhz with APs like Netgear R6300v2 which
do not publish support for 40Mhz but allow use of VHT in 20Mhz.
The break is because VHT is disabled once no HT cap doesn't indicate
support for 40Mhz. This causes the assoc request to be sent without
any VHT IE and the association is only HT due to this.

For more details check out commit 4a817aa7
"mac80211: allow VHT with peers not capable of 40MHz"

Fixes: 53b954ee4a71 ("mac80211: disable 40MHz support in case of 20MHz AP")
Signed-off-by: Eyal Shapira <eyalx.shapira@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>