SystemUI: Update cast tile when wifi display status changes

Cast tile in quick setting does not watch for wifi display status changes.
As a result, it will not update when wifi display status changes.

Register a broadcast to watch for wifi display status changes as settings
and update remote displays when wifi display status changes.

CRs-Fixed: 718032

Change-Id: Ib2ca4677be91817c007db941531849bbc7eff5d3