ath10k: fix band reporting for mgmt CCK frames on 5GHz

ath10k: fix band reporting for mgmt CCK frames on 5GHz

Although CCK modulation isn't expected for 11a if
it happened it made ath10k report wrong band
(2GHz) for a mgmt frame that were actually
received on 5Ghz band. Frequency would also
decoded incorrectly too.

In case of 5GHz-only devices this triggered
mac80211 WARN_ON because there was no according
sband pointer to be found.

The patch should fix delivery of such frames by
using different means to acquire band parameter.

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