ath10k: enable multi-channel on supported devices

This effectively enables multi-channel operation
on qca6174 WLAN.RM.2.0-00073 (and possibly any
newer firmware release for qca6174).

This adds appopriate interface combinations and
initializes firmware channel scheduler.

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