mac80211: add to bss_conf if broadcast TWT is supported

Add to struct ieee80211_bss_conf a twt_broadcast field.
Set it to true if both STA and AP support broadcast TWT.

Signed-off-by: Shaul Triebitz <shaul.triebitz@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20210618133832.f7c105237541.I50b302044e2b35e5ed4d3fb8bc7bd3d8bb89b1e1@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>