mac80211: fix 80 MHz association to 160/80+80 AP on 6 GHz

When trying to associate to an AP support 180 or 80+80 MHz on 6 GHz with a
STA that only has 80 Mhz support the cf2 field inside the chandef will get
set causing the association to fail when trying to validate the chandef.
Fix this by checking the support flags prior to setting cf2.

Fixes: 57fa5e85 ("mac80211: determine chandef from HE 6 GHz operation")
Signed-off-by: John Crispin <john@phrozen.org>
Link: https://lore.kernel.org/r/20200918115304.1135693-1-john@phrozen.org


[reword commit message a bit]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>