rsi: fix for 40MHZ connection issue.

Radio capabilities packet is not prepared properly for 40MHZ case,
ppe_ack_rate is a two byte variable which is initialized wrongly,
hence we are unable to connect, resolved by assigning it properly.

Signed-off-by: Ganapathi Raju <ganapathi.kondraju@redpinesignals.com>
Signed-off-by: Sushant Kumar Mishra <sushant.mishra@redpinesignals.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>