Merge changes from topic "gralloc-no-ion" into udc-dev

* changes:
  gralloc4: Choose framebuffer-secure for FB if available
  gralloc4: Remove redundant ion_device class and stale comments
  gralloc4: Remove dependence on libion_google
  gralloc4: Import system and vscaler heap from libion
  gralloc4: Remove dead code from ion