hwc: Handle layers marked as PROTECTED flag as secure

- All secure layers are marked with GRALLOC_USAGE_PROTECTED,
  irrespective of L1/L3, which should not fallback to GPU.
- In HWC, treat this layer as secure so that any fallbacks
  will be avoided.

Change-Id: I399740bfb5910f3fda4c4f395e2f7b49ea8619a9
Crs-fixed: 842071
3 files changed