nl80211: Remove AP mode interface from bridge for STA-mode-scan

nl80211: Remove AP mode interface from bridge for STA-mode-scan

Linux bridging code does not allow a station mode WLAN interface in a
bridge and this prevents the AP mode scan workaround from working if the
AP interface is in a bridge and scanning can be only done by moving to
STA mode. Extend this workaround to remove the interface from the bridge
temporarily for the duration of the scan, i.e., for the same duration as
the interface needs to be moved into the station.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>