surfaceflinger: Add missing code in opaque check

 * Add back the missing code for non QTI_BSP cases. Without it,
   this whole section is skipped, and horrible black screen flashing
   is seen on QCOM A fam, and probably on other platforms as well.

Change-Id: Ie39de7df4f1276be68aa4b1668e687f7a41b5625