bluedroid: fix several issues to enable a bluetooth device

bluedroid: fix several issues to enable a bluetooth device

* init_rfkill(): use the first rkilll interface (eeepc-bluetooth)
* set_bluetooth_power(): check the rfkill state before set it. If the
  state is already the expected value, don't write to it. This avoids
  the permission issue after wakeup for external bluetooth dongle.
* bt_enable(): try to disable and re-enable eeepc-bluetooth if unable
  to turn on it, since the rfkill id may has changed.