ath6kl: Fix AP mode connect event parsing and TIM updates

This cleans up the connect event parsing by defining a union in
struct wmi_connect_event to match with the three possible sets of
fields that the target uses depending on which type of connect
event is being indicated. In addition, two AP cases are now
separated from ath6kl_connect_event() so that correct field names
can be used to make it actually possible to understand what the
code is doing.

The bug hiding in the previous mess was in parsing the AID incorrectly
when processing the new station connecting event in AP mode. The fix
here for that is also fixing TIM updates for PS buffering to use the
correct AID.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>