ath10k: handle FW API differences for scan structures

The wmi_start_scan_cmd has an extra filed in our main
firmware track, reflact that to not have a mismatch in
case of 10.x track.

Signed-off-by: Bartosz Markowski <bartosz.markowski@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>