hwc: Set HPD once at boot up

- HPD has to be set only once during boot up.
- This also helps in use case where HPD is turned off
  (on purpose)through by adb shell for power testing
  and on suspend/resume, it gets re-enabled.

Change-Id: I7bf6fdd08e719432029c5d6e5756685d36cdca43

libhwcomposer/hwc_utils.cpp

@@ -413,6 +413,7 @@ void initContext(hwc_context_t *ctx)
     }
 
     memset(&(ctx->mPtorInfo), 0, sizeof(ctx->mPtorInfo));
+    ctx->mHPDEnabled = false;
     ALOGI("Initializing Qualcomm Hardware Composer");
     ALOGI("MDP version: %d", ctx->mMDP.version);
 }