gralloc: Add workaround for Jellybean camera drivers

* Arcee is smarter than I am, and discovered that we can simply swap
  two fields to ensure compatibility with Jellybean camera drivers
  having the metadata fields in the private_handle_t struct.
* Enable this by defining QCOM_BSP_CAMERA_ABI_HACK.

Change-Id: I2cd267dd5550404cf2e61d76fb805e780cd99d3c
display: Add flag to allow legacy allocations from MM heap

 * New devices with IOMMU use the MM heap exclusively for protected
   buffers. We need to support the old behavior for devices with legacy
   userspace.
 * Enable the old behavior with TARGET_DISPLAY_INSECURE_MM_HEAP.

Change-Id: I7882354fa8f159c707be11d7021c18561abfb522