ath11k: add HE support

Add basic HE support to the driver. The sband_iftype data is generated from
the capabilities read from the FW.

Signed-off-by: Shashidhar Lakkavalli <slakkavalli@datto.com>
Signed-off-by: John Crispin <john@phrozen.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>