ath11k: Send multiple scan_chan_list messages if required

With addition of 6Ghz channels, it is possible that wmi buffer size can
exceed the maximum wmi buffer size. So iterate over the channel list,
and send multiple messages till channel list is empty.
Also mark PSC channel flag for 6GHz channels accordingly.

Signed-off-by: Pradeep Kumar Chitrapu <pradeepc@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200603001724.12161-8-pradeepc@codeaurora.org