ath10k: fix RX performance when using AP 10.X FW

Due to oversight AP 10.X support was merged with
Ethernet RX decap mode.

Only Native Wifi RX decap mode guarantees IP
header is properly aligned and avoids sk_buff data
realignment (which is very expensive
performance-wise) in mac80211.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>