ath10k: WMI overhaul

Sync with internal WMI changes.

Signed-off-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
ath10k: Reduce maximum VDEV count

Fix this at 8 until the large-ap feature is ported to ath10k.
Tested with FW ver 604 using CUS223 v1 and v2.

Signed-off-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>