ath10k: implement channel switching

Until now channel change wasn't propagating to FW
directly because operational channel is abstracted
by VDEVs and it wasn't really necessary since
ath10k implements hwscan and hwroc.

This effectively fixes STA CSA and allows for
future AP-like CSA as well.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
ath10k: implement AP CSA

Most channel switching logic has been implemented
already so this patch is pretty small. The patch
makes use of mac80211's vif->csa_active for AP CSA
handling.

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