ath10k: configure rxnss_override for QCA9984

QCA9984 hardware can do 4x4 at 80Mhz, but only 2x2 at 160Mhz.

First, report this to user-space by setting the max-tx-speed
and max-rx-speed vht capabilities.

Second, if the peer rx-speed is configured, and if we
are in 160 or 80+80 mode, and the peer rx-speed matches
the max speed for 2x2 or 1x1 at 160Mhz (long guard interval),
then use that info to set the peer_bw_rxnss_override appropriately.

Without this, a 9984 firmware will not use 2x2 ratesets when
transmitting to peer (it will be stuck at 1x1), because
the firmware would not have configured the rxnss_override.

Signed-off-by: Ben Greear <greearb@candelatech.com>
[sven.eckelmann@openmesh.com: rebase, cleanup, drop 160Mhz workaround cleanup]
Signed-off-by: Sven Eckelmann <sven.eckelmann@openmesh.com>
[kvalo@qca.qualcomm.com: use hw_params, rename the title]
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>