ath10k: add VHT160 support

This patch adds full VHT160 support for QCA9984 chipsets Tested on Netgear
R7800. 80+80 is possible, but disabled so far since it seems to contain
glitches like missing vht station flags (this may be firmware or mac80211
related).

Signed-off-by: Sebastian Gottschall <s.gottschall@dd-wrt.com>
[kvalo@qca.qualcomm.com: refactoring and fix few warnings]
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>