ath6kl: reconfigure RSN capabilities when restarting AP

If the firmware decides to initiate a channel switch on an AP vif
running an RSN BSS, reconfigure the saved RSN IE capabilities as well.

Fixes a bug where the beacon and 4-way handshake would have a capability
mismatch after a channel switch, since the firmware apparently clears
these on an AP disconnect.

Signed-off-by: Thomas Pedersen <c_tpeder@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>