ath6kl: Fix BSS update on roaming

This fixes the BSS "update" just before the connected or roamed event.
The previous implementation was completely broken: it forced a hardcoded
signal strength and IEs from Association _Request_ frame instead of any
Beacon information. This broke various things, including PMKSA caching.

The current workaround for creating a dummy BSS entry before the roamed
event is not exactly ideal, but that is quite a bit better than the
previous state. As a future improvement, cfg80211 could potentially be
extended to allow this type of use or ath6kl could delay sending the
roamed event before receiving a BSS info event.

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