wifi: mac80211_hwsim: Use wider regulatory for custom for 6GHz tests

If a custom regulatory is being used, use the 6GHz regulatory for
testing 6GHz channels.

Signed-off-by: Chaitanya Tata <Chaitanya.Tk17@gmail.com>
Link: https://msgid.link/20240417074022.423432-1-Chaitanya.Tk17@gmail.com


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