surfaceflinger: Don't allow QC HWC virtual display without QC HWC copy

* QC media encoder appears to be incapable of switching between RGBA8888
  buffers and NV12_ENCODEABLE dynamically. This requires that we switch
  the entire stack to use the QC opaque format, or RGBA8888.

REF: CRACKLING-938
Change-Id: Ibd6a8faf8d268d3bfb4d61e4118a778ed82f1ab5