wifi: add rx filter init to fix broken unicast/broadcast (tiwlan)

- rx filters were broken for older tiwlan driver that expects
  unicast and broadcast filters to be added
- after an UPnP app was started (causing rx filtering enabled),
  both unicast and broadcast data packets were being dropped till
  wifi driver restart
- TODO: this should be better done directly in the driver code, but
  I haven't seen a clean way how to do it, so it's done in framework
  for now

Change-Id: I061eb8b231b8f158cf0ccbee637f2a4e6331b1fb