SurfaceFlinger: Make secure display ifdefs more narrow.

  * apq8084 target hals do not export display attrs
   the same as previous platforms (8974, 8960 etc)
   but continue the use of QCOM_BSP.
  * Due to this difference secure content is non-visible
   on apq8084 platforms because SF pushes the rendering
   to GLES vice the secure buffer of HWC and MDP.

Change-Id: Ie078638b1e22d1c9f73441e290c2882b4081b294