qtnfmac: do not cache BSS state in per-VIF structure

This cached state is used only once immediately after it is
initilized, except for BSSID value that is used for events processing.
There is no reason in keeping unused data in driver's state.

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