minigbm: add the BO_USE_RENDERSCRIPT flag back in

minigbm: add the BO_USE_RENDERSCRIPT flag back in

Previously, we mapped BO_USE_RENDERSCRIPT to BO_USE_LINEAR,
which made sense at the moment. However, we know have a case
where we need to special things with renderscript buffers on
ARM boards. Let's add back in the flag so we can differentiate
between normal linear buffers and renderscript buffers at map
and unmap time.

BUG=b:38097499
TEST=run cts -m CtsViewTestCases -t android.view.cts.SurfaceViewSyncTests
     passes on 9776.0.0 veyron_minnie

Change-Id: I7f1ee76735280ab6495a2d4af332cce5bc1c1727
Reviewed-on: https://chromium-review.googlesource.com/602735
Commit-Ready: Gurchetan Singh <gurchetansingh@chromium.org>
Tested-by: Gurchetan Singh <gurchetansingh@chromium.org>
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>