Enable TWT responder AP role only if IEEE 802.11ax/HE is enabled

Enable TWT responder AP role only if IEEE 802.11ax/HE is enabled

Set TWT responder configurator in the driver parameters only when the AP
is configured with HE enabled. This was already done for the extended
capability bit generation in commit 8de0ff0fa1de ("HE: Add TWT responder
extended capabilities field"), but this parameter for the driver command
to start the AP in _ieee802_11_set_beacon() missed the condition.

Move the ieee80211ax check into the common helper function to cover both
cases. In addition, add a check for disable_11ax to cover the case where
HE is disabled for a specific BSS.

Fixes: ab8c55358e10 ("HE: Dynamically turn on TWT responder support")
Signed-off-by: Jouni Malinen <quic_jouni@quicinc.com>