qtnfmac: do not cache AP settings in driver structures

Cached AP setings are passed to WiFi card right after they are
initialized and are never used for anything else. There is no
point in keeping them in driver state.

Signed-off-by: Igor Mitsyanko <igor.mitsyanko.os@quantenna.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>