mapped_access_perf_test: Fix buffer overwrite

In NV12Rotate90, treat the UV buffer as an array of uint16 rather than
an array of uint8.

BUG=b:188094595
TEST=Run on grunt

Change-Id: I096c3d3955fc79a7c197c4f9d3411fd4a5e56159
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/drm-tests/+/3022569
Tested-by: Drew Davenport <ddavenport@chromium.org>
Commit-Queue: Drew Davenport <ddavenport@chromium.org>
Reviewed-by: Miguel Casas <mcasas@chromium.org>
1 file changed