nl80211: really allow client-only BIGTK support

My previous commit here was wrong, it didn't check the new
flag in two necessary places, so things didn't work. Fix that.

Fixes: 155d7c73 ("nl80211: allow client-only BIGTK support")
Link: https://lore.kernel.org/r/20200528213443.993f108e96ca.I0086ae42d672379380d04ac5effb2f3d5135731b@changeid


Signed-off-by: Johannes Berg <johannes.berg@intel.com>