wifi: set the BridgeIfname supplicant property when needed
When a wifi device is in a bridge, the supplicant must be aware of it, as a socket must be opened on the bridge to receive packets.
Set the BridgeIfname property of the supplicant Interface object before starting the association. Note that the property was read-only in the past and recently  became read-write. When using a supplicant version without the patch, writing the property will return an InvalidArgs error and NetworkManager will print a warning.