ath10k: handle channel change htt event

Whenever firmware is configuring operating channel during scan or
home channel, channel change event will be indicated to host. In some
cases (device probe/ last vdev down), target will be configured to
default channel whereas host is unaware of target's operating channel.
This leads to packet drop due to unknown channel and kernel log will be
filled up with "no channel configured; ignoring frame(s)!". Fix that
by handling HTT_T2H_MSG_TYPE_CHAN_CHANGE event.

Signed-off-by: Rajkumar Manoharan <rmanohar@qti.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>