ath10k: set rxnss_override for QCA9888

QCA9888 supports VHT80 with 2x2. But it only support 1x1 with VHT160 or
VHT80+80. Inform userspace and the the QCA firmware about that limitation
whenever VHT80+80 or VHT160 is configured.

Signed-off-by: Sven Eckelmann <sven.eckelmann@openmesh.com>
[kvalo@qca.qualcomm.com: use hw_params]
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>