qtnfmac: implement dump_station support for STA mode

Current implementation of dump_station cfg80211 callback supports
AP mode only. Add support for STA mode as well: by default in STA
mode this callback is supposed to return AP on managed interface.

Signed-off-by: Sergey Matyukevich <sergey.matyukevich.os@quantenna.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>