ath10k: clear htt->rx_confused on load

Once driver entered the rx_confused state it would
refuse to rx even after firmware is restarted.
Make sure to clear it so that rx works after, e.g.
hw restart or after all interfaces are stopped.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>