tf700t: add NULL value to bluedroid build config

Change-Id: I00d30ce10eff500f9e178da6f2ef014f0bee56e2
tf700t: enable TARGET_RUNNING_WITHOUT_SYNC_FRAMEWORK target

  If we don't have the sync framework we will never have
  addPresentFence called.  This means we have no way to know whether
  or not we're synchronized with the HW vsyncs, so we just request
  that the HW vsync events be turned on whenever we need to generate
  SW vsync events.

Change-Id: I92aa8213cc93209d5642a1b5325d63bd1c3b288d