wifi: mac80211: advertise TWT requester only with HW support

Currently, we rely only on the AP capability. If the AP supports
TWT responder we will advertise TWT requester even if the driver
or HW doesn't support it. Fix this by checking the HW capability.

Signed-off-by: Haim Dreyfuss <haim.dreyfuss@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>