Set HAL path to display-caf-kk_2.7

Set display variant to caf-kk_2.7 to build this HAL.
hwc: Get the retire fence from the MDP driver

Get the retire fence separately instead of duplicating the
release fence.

Bug: 9319776
Change-Id: Iacb773c2d94f635e27a7b355d399cb2e36dac2a5
Signed-off-by: Iliyan Malchev <malchev@google.com>
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
display: Properly handle NO_IOMMU case

 * Enable it by default for msm8660 too.

Change-Id: Icbd5de1e7f020285ff6101c34286ca8863b11040
display: Don't push to MM heap for NO_IOMMU for display buffers

Change-Id: I30a8280099aa82e9b3e9754a4a68ad6a81f705f7