libgralloc: Fix secure buffer issues.

-- Though buffer usage is not marked with any Heap, if usage flags
set with GRALLOC_USAGE_PROTECTED allocate from IOMMU heap.
-- Allow using  GRALLOC_USAGE_PROTECTED for non tz level protection.

Change-Id: Ie3c8bd8821f4ab344a2b798a723ab65d4ef5b44e
CRs-fixed: 484838
CRs-fixed: 480493
2 files changed