ath10k: add spectral scan support to wmi-tlv

Command structure and event flow doesn't seem to
be any different compared to existing
implementation for other firmware branches.

This patch effectively adds in-driver support for
spectral scanning on QCA61x4 and QCA9377.

Tested QCA9377 w/ WLAN.TF.1.0-00267-1.

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