wifi: mwifiex: cleanup struct mwifiex_private

Remove set but otherwise unused 'adhoc_is_link_sensed' and
'assoc_resp_ht_param' members of 'struct mwifiex_private' and
simplify related code in 'mwifiex_ret_802_11_associate()'.
Compile tested only.

Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://patch.msgid.link/20240927084317.96687-2-dmantipov@yandex.ru